GMC Code P1390: CKP/CMP Synchronization Error – Complete Diagnosis

The P1390 code on GMC vehicles (Sierra, Yukon, Canyon, Acadia) indicates a critical misalignment between the crankshaft (CKP) and camshaft (CMP), compromising engine control. Common on Vortec V8 and LLT V6 engines, this fault requires immediate attention to prevent engine destruction.

🚨 Immediate Symptoms

  1. Failure to start or sudden engine stalling.
  2. Severe jerking during acceleration + loss of power.
  3. Flashing “Check Engine” light (related codes: P0016, P0340).
  4. Metallic rattling near the timing cover (loose chain).

🔧 Specific GMC Causes

  1. Stretched timing chain (very common on 5.3L/6.2L V8 engines with over 100,000 km).
  2. Faulty hydraulic tensioner (internal leak or broken spring).
  3. Defective CKP/CMP sensor (flooded by oil leaks).
  4. Cracked or dirty reluctor wheel (missing teeth, magnetic debris).
  5. Insufficient oil pressure (failed pump, clogged filter, degraded oil).

🔍 Step-by-Step Diagnosis

  1. Check oil pressure:
    • Minimum: 12 psi at idle, 40+ psi at 2,000 RPM (using ACDelco T-80 gauge).
  2. Inspect the timing chain:
    • Access via side cover (on Sierra 1500, Yukon XL models).
    • Check timing mark alignment (misalignment > 6° = danger).
  3. Test the sensors:
    • CKP: Resistance 850–1350 Ω (V8 5.3L).
    • CMP: AC 0.5–3V signal on oscilloscope.
  4. Advanced GM scan:
    • Use Tech2/GDS2 to analyze CKP/CMP misalignment (> 2° = confirmed fault).

🛠️ Recommended Repairs (With ACDelco/GM References)

Faulty Component Solution OEM Parts
Timing chain Replace complete kit (chain + tensioners + guides) ACDelco 12640486 (5.3L V8)
Hydraulic tensioner Replace + check oil circuit GM 12633825
CKP sensor Replace (air gap: 0.5–1.5 mm) ACDelco 213-1151
CMP sensor Clean or replace Delphi FG1105 (V6 3.6L)
Reluctor wheel Replace crankshaft reluctor ring GM 12586459

⚠️ Critical Warning:
Ecotec and Vortec engines are interference engines! Desynchronization causes piston-to-valve contact. Stop the engine immediately!

💡 Key Post-Repair Procedures

  1. Timing alignment:
    • GM tools: Crankshaft lock tool J-42386 + Camshaft lock tool J-45027.
  2. ECU reset:
    • Clear codes via Tech2 + sensor relearn procedure.
  3. Oil maintenance:
    • 5W-30 Dexos1 (e.g., Mobil 1 ESP) + GM filter PF64.

📊 Technical Sheet

Parameter Value
OBD2 Code P1390
Definition “Crankshaft/Camshaft Position Sensor Correlation Error”
Sensitive Models Sierra, Yukon, Acadia, Canyon (2007–2022)
Urgency MAXIMUM (risk of engine failure)

Recurring Problems by Model

Model Common Failure Solution
Sierra 1500 5.3L Stretched chain (cold start rattling) ACDelco kit 12640486
Yukon 6.2L V8 Seized hydraulic tensioner Replace GM 12633825
Acadia 3.6L V6 Dirty CMP sensor (camshaft seal leak) Delphi FG1105 + seal 12688049

Exclusive GMC Technical Tips

  1. Software update:
    • On Sierra 2014–2018, an ECU reflash (TSB 18-NA-355) sometimes fixes false P1390 codes.
  2. Check oil filter:
    • Non-OEM filters (PF64 required) clog tensioner oil passages.
  3. Leak inspection:
    • A leaking rocker cover gasket floods CMP sensors (GM seal 12688049).

Conclusion

The P1390 code on GMC indicates a critical engine desynchronization. Proceed in 3 steps:

  1. Stop the engine and check oil/pressure (risk of immediate failure).
  2. Inspect the timing system and CKP/CMP sensors (80% of cases).
  3. Replace faulty components with ACDelco/GM parts and recalibrate with Tech2.

🔧 Average repair cost:

  • Timing chain: $800–$2,000
  • Sensors + labor: $300–$600
    Do not drive – have it towed to a certified GM technician. Ignoring it can cost $5,000+ (engine replacement).

Honda Code P1390: Variable Valve Timing (VTEC) Problem – Diagnosis and Solutions

Introduction

The error code P1390 is specific to Honda and Acura vehicles. It indicates an anomaly in the camshaft position circuit (Bank 1), related to the VTEC system (Variable Valve Timing and Lift Electronic Control). This system optimizes engine performance and efficiency by adjusting valve timing. Ignoring this code can lead to power loss, increased fuel consumption, or engine damage.

VTEC Operation: Technical Overview

The VTEC system uses pressurized engine oil to activate a mechanism that changes the camshaft profile:

  • At low RPM: “Mild” profile for fuel economy.
  • At high RPM: “Aggressive” profile to increase power.
    The P1390 code occurs when the PCM (Powertrain Control Module) detects an abnormal discrepancy between the signals from the camshaft position sensor (CMP) and the crankshaft position sensor (CKP).

Possible Causes of P1390

  1. Engine Oil Issues:
    • Low oil level.
    • Degraded oil or incorrect viscosity (e.g., not using 5W-30).
    • Clogged oil filter or VTEC filter (due to deposit buildup).
  2. Electrical Failures:
    • Faulty VTEC solenoid (most common).
    • Failed camshaft position sensor (CMP).
    • Damaged wiring (short circuits, corrosion).
  3. Mechanical Problems:
    • Weak oil pump (insufficient pressure).
    • Worn or stuck VTEC gears.
    • Internal oil leaks in the VTEC mechanism.
  4. PCM Errors (rare):
    • Software or hardware failure of the control module.

Common Symptoms

  • 🚨 Check Engine light illuminated.
  • 🐌 Power loss (especially at high RPM).
  • 🔉 Clicking or abnormal noises from the engine.
  • ⛽ Increased fuel consumption.
  • ⚠️ Unstable idle or stalling.

Step-by-Step Diagnosis

  1. Check Engine Oil:
    • Inspect level and quality. Replace if necessary with recommended oil (e.g., 5W-30).
  2. Scan for Related Codes:
    • Look for associated codes (e.g., P0341, P2646) to refine diagnosis.
  3. Inspect VTEC Solenoid:
    • Electrical Test: Measure resistance (normal range: 14–30 Ω).
    • Functional Test: Apply 12V to check for a “click” sound.
    • Clean VTEC Filter (located under the solenoid).
  4. Check Oil Pressure:
    • Use a pressure gauge (target: 40–80 psi at 3,000 RPM).
  5. Inspect Sensors and Wiring:
    • Check CMP and solenoid connectors. Test wire continuity.
  6. Analyze Live Data:
    • Observe CMP/CKP signals with an oscilloscope (look for discrepancies).

Repair Solutions

Cause Solution Estimated Cost
Low/degraded oil Oil change + oil filter. 50–100 €
Faulty VTEC solenoid Replace solenoid (OEM: 31110-PAA-003). 80–200 € (part)
Clogged VTEC filter Clean or replace. 5–20 €
Faulty CMP sensor Replace sensor. 60–150 €
Weak oil pump Replace pump (requires engine disassembly). 400–800 €
Damaged wiring Repair wires or replace harness. 50–300 €

Common Mistakes to Avoid

  • Neglecting the VTEC filter (small but critical!).
  • Using non-compliant oil not meeting Honda specifications.
  • Forgetting to reset the PCM after repair (via OBD2 scanner).

Conclusion

The P1390 code is often related to neglected maintenance (oil or filters). Start with simple checks (oil level, VTEC filter) before exploring complex causes (oil pump, PCM). Prompt action prevents costly damage to the VTEC system. If diagnostic steps exceed your skills, consult a Honda/Acura specialist mechanic.

Tip: Perform regular oil changes with quality oil to prevent 70% of P1390 occurrences!

Understanding the P1391 Code (CMP Sensor Correlation Fault)

Code P1391 (sometimes listed as P1391 00 in modern OBD-II systems) is an error code related to engine timing. It signals a correlation problem between the crankshaft position sensor (CKP) and the camshaft position sensor (CMP). This fault can lead to critical malfunctions such as stalling, misfires, or hard starting.

Technical Meaning

  • OBD-II Definition:
    “Crankshaft Position Sensor / Camshaft Position Sensor – Correlation”.
    The engine control unit (ECU) detects an abnormal discrepancy between the signals from the two sensors, which are essential for controlling injection and ignition.
  • Consequences:
    Misalignment disrupts valve timing and injection, risking engine damage (e.g., piston/valve collision in interference engines).

Possible Causes

  1. Mechanical Issues:
    • Loose, worn, or improperly timed timing belt/chain.
    • Faulty CKP/CMP alignment sprocket.
    • Slippage of the camshaft variator (in VVT systems).
  2. Electrical Failures:
    • Faulty CKP or CMP sensor (cut wires, oxidized connector).
    • Damaged or dirty reluctor wheel (magnetic target).
  3. Other Causes:
    • Poor quality engine oil (affects VVT systems).
    • Voltage issue (weak battery, faulty alternator).

Common Symptoms

  • 🚨 Check Engine Light (MIL) illuminated.
  • 🔧 Misfires and power loss.
  • 💨 Overheating or abnormal exhaust smoke.
  • 🔋 Hard starting (engine cranks but won’t start).
  • ⚠️ Stalling at low RPM or during acceleration.

Diagnostic Procedure

  1. Code Reading:
    Use an OBD-II scanner to check for associated codes (e.g., P0016/P0017).
  2. Visual Inspection:
    • Check the timing belt/chain (tension, alignment).
    • Inspect sensor cables and connectors.
  3. Electrical Tests:
    • Measure CKP/CMP sensor resistance (typical value: 500–1500 Ω).
    • Analyze the signal with an oscilloscope (sine or square wave).
  4. Mechanical Check:
    • Verify camshaft alignment with a dedicated locking tool.
    • Examine the crankshaft reluctor wheel (cracks, dirt).

Repair Solutions

  • Sensor Replacement (CKP/CMP): Average cost €80–150 (part).
  • Timing Realignment:
    • Replacement of timing belt/chain + timing kit: €400–900.
    • Verification of sprocket alignment.
  • Reluctor Wheel Cleaning/Replacement: If magnetic and dirty.
  • ECU Update: If software error (rare cases).

⚠️ Important: A P1391 error requires professional diagnosis. Attempting repair without expertise may worsen damage (e.g., engine failure).

Case Studies

  • Volkswagen Golf 1.9 TDI (2005): P1391 code caused by a cracked reluctor wheel on the crankshaft → Flywheel replacement.
  • Toyota Corolla VVT-i (2012): Timing drift due to a stuck camshaft variator → VVT system cleaning + appropriate engine oil.

FAQ

Q1: *Can I drive with a P1391 code?*
→ Not recommended. Risk of stalling or engine damage.

Q2: *Does a faulty sensor always trigger P1391?*
→ Yes, but check the timing first (most common cause).

Q3: Average repair cost?
→ €200–1000 depending on the cause (sensors vs. timing).

Conclusion

Code P1391 is a serious alert regarding engine timing integrity. Although sometimes related to simple sensors, it often hides critical mechanical issues (timing). Precise diagnosis by a professional is essential to avoid costly repairs. If this code appears, stop the vehicle and consult a garage immediately.

P1391 Acura Code: CKP/TDC Sensor Synchronization Fault

On Acura (particularly models with Honda K-series engines like the RSX, TL, TSX), the P1391 code indicates an inconsistency between the signals from the crankshaft position sensor (CKP) and the camshaft position sensor (CMP). This fault disrupts the management of timing and injection.

Common Causes on Acura

  1. Faulty CKP/CMP Sensors:
    • Wear or contamination by oil/metal (common on K20/K24 engines).
    • Oxidized connectors (especially in humid climates).
  2. Timing Issues:
    • Slack timing chain (models without a belt).
    • Stuck VTC (Variable Timing Control) sprockets (carbon deposits).
  3. Mechanical Components:
    • Damaged crankshaft reluctor wheel (cracks, deformation).
    • Oil pump problem (insufficient pressure affecting VTC).
  4. Electrical Failures:
    • Rubbed or cut wiring near the engine block.
    • Poor connection at the PGM-FI relay (injection system).

Typical Symptoms on Acura

  • 🚨 Persistent “Check Engine” light.
  • 🔧 Misfires at idle (especially on Acura RSX Type-S).
  • 🌀 Loss of power and hesitant acceleration.
  • ⚠️ Hard starting (abnormal knocking).
  • ⚡ Excessive fuel consumption.

Acura-Specific Diagnostic

  1. Advanced OBD-II Scanner:
    • Check live data: CKP/CMP deviation > 5°.
    • Look for associated codes (P0341, P0339).
  2. Visual Inspection:
    • Inspect CKP/CMP sensors (located on the driver’s side near the flywheel).
    • Check the VTC sprocket tightness (access via timing cover).
  3. Key Tests:
    • CKP/CMP resistance: 450–700 Ω (out of tolerance = faulty).
    • Oscilloscope signal: Missing peak = damaged reluctor wheel.
  4. Oil Pressure:
    • Measure with a pressure gauge (target: > 35 psi at idle).

Common Repairs

Cause Solution Average Cost
Faulty CKP sensor Replace (OEM: Honda 37870-PRB-A01) 80–150€ + labor
Faulty CMP sensor Cleaning or replacement 70–130€
Loose timing chain Replace chain + tensioner 600–900€
Stuck VTC sprocket Disassembly/cleaning or replacement 200–500€
Damaged reluctor wheel Replace flywheel (extreme case) 400–800€

Common Cases by Model

  • Acura RSX (2002–2006):
    P1391 often related to the CKP sensor or a VTC misalignment after timing service.
  • Acura TL (3G, 2004–2008):
    Recurring issues with CKP wiring chewed by rodents or oxidized.
  • Acura TSX (2004–2008):
    Code triggered by a worn oil pump → insufficient pressure for VTC.

Acura Technical Tips

  1. ⚠️ Do not ignore the code: Risk of unexpected stalling or VTC damage.
  2. Post-repair reset:
    • Clear the code with a scanner + idle learn procedure (10 min with warm engine).
  3. Use OEM parts:
    • Generic sensors often cause recurring issues on Acura.

In Summary

P1391 on Acura generally points to:

🔧 1 faulty CKP/CMP sensor (50% of cases)
⚙️ 2 a timing/VTC issue (30% of cases)
🔌 3 an electrical problem (20% of cases).

A thorough inspection of the timing system and electrical signals is crucial. If the fault persists after replacing sensors, check the ECU power supply voltage and engine ground. Consult an Acura specialist for a precise diagnosis if necessary.

P1391 Audi Code: PMH/PMB Synchronization Fault

At Audi, code P1391 (or P1391 00) indicates a critical discordance between the signals from the crankshaft sensor (G28) and the camshaft sensor (G40). This fault disrupts the management of timing, injection, and ignition, particularly on TFSI/TDI engines equipped with VVT (Variable Valve Timing) systems.

Common Causes on Audi

  1. Mechanical Problems (50% of cases):
    • Slack timing chain (faulty hydraulic tensioner on 2.0 TFSI engines, e.g., EA888).
    • VVT sprocket misalignment (carbon deposits locking the variator).
    • Damaged crankshaft tone wheel (cracks on dual-mass flywheel).
  2. Electrical Failures (30%):
    • Faulty G28 or G40 sensor (often after engine disassembly).
    • Chewed/corroded wiring (especially near the engine block or rear harness).
    • Engine ground issue (corrosion at the anchor point near the battery).
  3. Other (20%):
    • Degraded engine oil (unsuitable viscosity or exceeded oil change interval).
    • Weak oil pump (insufficient pressure for VVT).
    • Faulty engine control unit (ECU) (rare cases, requires advanced diagnostics).

Specific Audi Symptoms

  • 🚨 Check Engine Light + ESP Light on (stability control deactivated).
  • 🔧 Misfires at idle (especially on Audi A4/A5/Q5 with 2.0 TFSI engine).
  • ⚠️ Sudden stalling during acceleration.
  • 🔊 Metallic rattling when cold (slack timing chain).
  • ⛽ Excessive fuel consumption (+15-20%).

Audi-Specific Diagnostics

  1. Required Tools:
    • VCDS (VAG-COM) or ODIS scanner to read measurement blocks (groups 090-093).
    • 4-channel oscilloscope (to compare G28/G40 signals).
  2. Key Parameters to Check:
    • Phase deviation TDC/BDC (target: < ±3°).
    • Oil pressure (minimum 2.0 bar at idle).
    • VVT angle (compare with factory values).
  3. Priority Tests:
    • Chain inspection: Check play with a timing tool (e.g., T40058 tool for EA888).
    • Electrical check:
      • G28/G40 sensor voltage: 5V (supply) / 0.1–4.8V (signal).
      • Resistance: 500–1000 Ω (out of tolerance = faulty).
    • Oil analysis: Presence of metal particles (indicates pump or chain wear).

Common Repairs & Costs

Cause Solution Average Cost (Audi)
Failed chain tensioner Replace chain + tensioner + guides 900–1,500 €
Faulty G28 sensor Replacement (Ref. 06H906433B) 120–200 €
Stuck VVT sprocket Ultrasonic cleaning or replacement (Ref. 06H109257) 300–600 €
Damaged tone wheel Flywheel replacement 800–1,400 €
Wiring issue Harness repair + heat sleeve 150–400 €

⚠️ Warning: On EA888 Gen 2/3 engines (Audi A3/TT), a P1391 can hide premature chain tensioner wear → Risk of engine failure!

Audi Case Studies

  1. Audi A4 B8 (2.0 TFSI):
    • Code P1391 + cold start rattling noise.
    • Cause: Failed chain tensioner → Timing kit replacement.
  2. Audi Q5 (3.0 TDI):
    • P1391 after timing belt replacement.
    • Cause: Incorrect BDC sprocket timing → Realignment with T10340 tool.
  3. Audi TT RS (EA855):
    • P1391 under acceleration.
    • Cause: G28 sensor flooded with oil (faulty seal) → Replacement + cleaning.

Post-Repair Procedure

  1. Reset adaptations:
    • Via VCDS: [Select engine] → [Adaptations] → Reset “Cam Angle”.
  2. Idle learning:
    • Let run for 10 min at 2,500 RPM, then stabilized idle.
  3. Road test:
    • Verify no code over 3 drive cycles.

Audi FAQ

Q1: Can I drive my Audi with a P1391?
→ Dangerous! Risk of engine failure (especially on TFSI) → Towing recommended.

Q2: Why does the code return after replacing sensors?
→ Imperatively check ECU supply voltage and mechanical timing.

Q3: Can a general mechanic repair it?
→ Only an Audi/VAG specialist masters the specific timing tools (e.g., T40267).

Conclusion

P1391 on Audi often signals critical timing wear or a complex electrical fault. Recent TFSI/TDI engines are particularly vulnerable.
Recommendations:

  1. Stop the vehicle immediately.
  2. Have the chain tension checked (timing tool mandatory).
  3. Prefer OEM parts (generic parts cause recurrences).

Fault Code P1391 Buick: Wheel Speed Sensor 1 (WSS) Circuit Issue

Critical Role of the Sensor ⚠️

In this article, we will examine the Fault Code P1391 and its impact on your vehicle’s operation.

To better understand this code, it is essential to look at the operation of the speed sensor. The latter is crucial for the vehicle’s active safety, as it allows various systems to function effectively. For example, a faulty sensor can lead to a loss of vehicle control, especially in adverse weather conditions. Indeed, during emergency braking, if the sensor does not transmit the correct information, the ABS system will not function as intended, increasing the risk of an accident.

Furthermore, the wheel speed sensor 1 also plays a role in optimizing fuel consumption. When the vehicle is properly equipped with a functional sensor, the engine control unit can adjust the engine’s performance in real-time, thus contributing to better fuel economy. Therefore, a faulty wheel speed sensor can not only compromise your safety but also increase your operating costs related to fuel.

The wheel speed sensor 1 (usually the front left wheel) provides vital data for:

  • ABS Braking (prevents wheel lock-up)
  • Traction Control (prevents loss of grip)
  • Directional Stability (ESC system)
  • Vehicle Speed Calculation (speedometer, engine management)

Main Causes 🔧

The Fault Code P1391 indicates a problem related to the wheel speed sensor 1, which can affect the systems mentioned above.

Frequency Cause Details
45% Sensor failure Damaged magnet, burnt-out coil (overheating/corrosion)
30% Wiring problems Cut wires, oxidized connectors (especially behind the wheel)
15% Dirty/damaged tone ring Grease/metal debris on the reluctor
7% Excessive bearing play Sensor-reluctor misalignment
3% ABS/ECM module failure Rare – requires in-depth diagnosis

It is also important to note that preventive sensor replacement can be beneficial. If you notice signs of failure, such as erratic behavior in the speedometer or warning lights illuminated, it is advisable to have the sensor inspected quickly. Indeed, this can help you avoid more costly repairs in the future and ensure your vehicle remains safe on the road.

The average lifespan of a wheel speed sensor is approximately 100,000 to 150,000 kilometers, but this can vary depending on several factors, including driving conditions and vehicle maintenance. Frequent driving in harsh conditions, such as muddy or snowy roads, can reduce the sensor’s lifespan. Therefore, it is wise to regularly check its condition, especially if you have noticed anomalies in the operation of your car’s safety systems.

Symptoms 🚨

  • ABS + Traction Control warning lights illuminated on the dashboard
  • ABS deactivated (traditional braking only → risk of hydroplaning)
  • Loss of stability control (dangerous turns in wet weather)
  • Erratic behavior of the speedometer
  • ⚡ Excessive fuel consumption (the ECM poorly compensates for data loss)

Another symptom to watch for is an unexpected variation in the speed displayed on the dashboard. This may indicate that the sensor is not working correctly or that there is a problem with the wiring. For example, if you accelerate, but the speedometer remains stubbornly low, this warrants immediate investigation. Drivers should be attentive to these warning signs to avoid more serious problems on the road.

Specific Buick Diagnostic 🔍

Step 1: Visual Inspection

  1. Locate the front left wheel sensor (behind the brake disc)
  2. Check:
    • Electrical connector (frequent corrosion on Buick Enclave/LaCrosse)
    • Sensor/reluctor distance (0.5-1.5 mm max)
    • Cleanliness of the tone ring (clean with degreaser if dirty)

Step 2: Electrical Tests

Test Tool Normal Values
Resistance Multimeter 800-1400 Ω (depending on model)
AC Voltage Oscilloscope (wheel rotating) Sinusoidal signal > 0.5V
Continuity Circuit tester No breaks to ABS module

During the visual inspection, it is also helpful to check the condition of other components associated with the safety systems, such as brake discs and pads. A braking system in good condition can compensate for some of the problems caused by a faulty speed sensor but should not be considered a long-term solution. Particular attention should be paid to the entire braking system to ensure vehicle safety.

Repairs & Costs 💰

Problem Solution Average Cost
Faulty Sensor Replacement (ACDelco/GM) $80-150 + labor
Damaged Wiring Harness repair $100-200
Tone Ring Cleaning/replacement $20-180
ABS Module Reprogramming/replacement $300-800

⏱️ Intervention Time: 1h (diagnosis) + 1h (simple repair).

Safety Emergencies 🚨

Do not drive if:

  • ABS + traction control warning lights are flashing
  • Abnormal grinding noises at low speed
  • Spongy brake pedal
    → Risk of complete deactivation of electronic aids!

In addition to electrical tests, it might be helpful to regularly monitor the vehicle’s performance over time. Noting changes in driving behavior can reveal trends that might indicate an emerging problem. For example, if you start to feel unusual vibrations while driving, this could be a sign that something else is wrong, possibly related to the speed sensor.

Electrical tests can also include evaluating the connections at the ABS module level, as connection problems can also disrupt the sensor’s operation. A multimeter can help you determine if the signal is being transmitted correctly. If the test reveals anomalies, it may be necessary to replace the wiring or connectors to restore optimal operation.

Pro Tips 🔧

When it comes to repairs, it is important to consider the warranties offered by the manufacturer on replacement parts. Sometimes, the initial cost of a high-quality sensor may be higher, but it is usually justified by increased durability and reliability. By investing in quality replacement parts, you can avoid recurring problems that could otherwise lead to additional costs in the long run.

  1. Universal Sensor: Avoid low-end parts (frequent calibration errors).
  2. Reset: After repair, clear codes via OBD-II + road test at 40 km/h.
  3. Sensitive Models: Buick Regal 2011-2017 (connector corrosion – seal with dielectric grease).
  4. Common Error: Confusing P1391 (circuit problem) with C1391 (internal ABS module fault).

📊 Statistic: 90% of P1391 codes on Buick are resolved by sensor replacement + reluctor cleaning.

Conclusion:
The P1391 code compromises active safety systems. Recommended procedure:

Replace the sensor if necessary → Reset the ECM
Do not ignore this code: a faulty ABS system triples the risk of accident in slippery conditions!

Check wiring and connector

Test the sensor (resistance/signal)

Clean the tone ring

In conclusion, it is essential to monitor the condition of your speed sensor and react quickly to signs of failure. Ignoring the Fault Code P1391 can have serious consequences for your safety and that of others on the road. In terms of prevention, regular maintenance and constant vigilance are your best allies to ensure your vehicle functions properly. Do not take a problem that may seem minor lightly, as it could quickly become a major danger. If you have any doubts, do not hesitate to consult a professional for a thorough diagnosis.

Chevrolet Code P1391: Performance of the G Sensor Circuit for Wheel Speed Sensor 1

🔍 Sensor Role

The Chevrolet Code P1391 is related to the performance of the G sensor circuit of the wheel speed sensor 1.

This code is an important indicator for Chevrolet vehicle owners, signaling a potential problem that could affect the vehicle’s safety and performance. Understanding the Chevrolet Code P1391 can help you make informed decisions regarding your car’s maintenance and repairs.

It is essential to know that the speed sensor is also used for the stability control system, which helps prevent skidding during difficult driving conditions. Proper functioning of this sensor can prevent accidents and improve the vehicle’s overall safety.

The wheel speed sensor 1 (usually the front left wheel) is critical for:

  • ABS Braking
  • Traction Control
  • Electronic Stability Control (ESC)
  • Speed Calibration (speedometer, transmission management)

⚠️ Immediate Symptoms

Another important point to consider is that the speed sensor plays a crucial role in the operation of modern driver assistance systems, such as adaptive cruise control. Any malfunction of this sensor could therefore disrupt these advanced features.

  • ABS + Traction Warning Lights illuminated on the dashboard
  • Deactivation of ABS Braking (risk of wheel lock-up)
  • Erratic behavior of the speedometer
  • Loss of stability control during turns
  • Possible engine stalling during acceleration (on automatic transmission models)

Drivers may also notice changes in their vehicle’s performance, such as less smooth acceleration or jerking while driving. These signs can often be attributed to a problem with the speed sensor.

Furthermore, if the ABS and traction warning lights come on, it is advisable to avoid driving the vehicle, as this could lead to dangerous situations. When these indicators appear, it is best to have the vehicle inspected immediately by a professional.

🔧 Common Causes on Chevrolet

Frequency Cause Sensitive Models
50% Faulty sensor Silverado, Tahoe, Equinox (2010-2018)
25% Damaged wiring Traverse, Malibu (connectors near wheel well)
15% Dirty/deteriorated tone ring Impala, Cruze (mud/grease buildup)
7% Mechanical play (bearing) Colorado, TrailBlazer
3% ABS module failure Rare cases – requires advanced diagnosis

🛠️ Diagnosis in 3 Steps

1. Visual Inspection (20 min)

  • Locate the front left wheel sensor (behind the brake disc).
  • Check:
    • Electrical connector (frequent corrosion on Silverado).
    • Sensor/reluctor gap (0.3–1.0 mm).
    • Cleanliness of the tone ring (clean with brake cleaner).

2. Electrical Tests

Test Tool Normal Values
Resistance Multimeter 850–1350 Ω (depending on model)
AC Voltage Oscilloscope Signal > 0.35V (wheel rotating at 60 rpm)
Power Supply DC Multimeter 12V with ignition ON

Diagnosing problems related to the speed sensor can be complex and often requires specific technical skills. Garages equipped with advanced diagnostic tools can quickly identify problems and provide appropriate solutions.

3. Advanced Scan

  • Use a GM MDI or Tech2 scanner to:
    • Read live data (wheel speeds compared).
    • Check for companion codes (e.g., C1391 = ABS module problem).

💰 Solutions & Costs

Problem Repair Average Cost
Faulty Sensor Replacement (ACDelco) $70–140 (part) + 0.5h labor
Damaged Wiring Harness repair $100–250
Tone Ring Cleaning/replacement $30–200
ABS Module Reprogramming/replacement $400–900

⏱️ Service Time: 1h (diagnosis) + 1h to 2h (repair).

🚨 Safety Emergencies

Do not drive if:

  • The ABS/traction warning lights are flashing.
  • Metallic grinding noises are heard at low speeds.
  • The steering becomes heavy during turns.
    → Risk of total loss of controlled braking!

In summary, it is crucial to pay attention to alerts regarding the Chevrolet Code P1391. Ignoring the symptoms and delaying repairs can lead to more serious problems and higher repair costs in the long term.

  1. Specific Parts:
    • ACDelco sensor 213-928 (Silverado) or 213-3065 (Equinox).
  2. Reset:
    • Clear codes via OBD-II + road test at 40 km/h (don’t forget sharp turns).
  3. Anti-corrosion:
    • Apply dielectric grease to connectors (especially on Cruze/Impala).
  4. Common Mistake:
    • Do not confuse P1391 (circuit problem) with P1392 (intermittent signal).

📊 Workshop Data: 80% of P1391 codes on Chevrolet resolved by sensor replacement + reluctor cleaning.

Conclusion:
A P1391 code on Chevrolet disables vital safety systems. Recommended procedure:

  1. Check front left wheel wiring and connector.
  2. Test the sensor (resistance/signal).
  3. Clean/adjust the tone ring.
  4. Replace the sensor if necessary → Reset the ECM.
    Do not ignore this code: A faulty ABS increases braking distances by 30% on wet roads!

It is also recommended to keep records of previous repairs and error codes. This can help technicians better understand the vehicle’s history and avoid redundant diagnostics.

As vehicles age, it is normal for some parts to start showing signs of wear. Regular maintenance can help detect problems before they become serious. This includes checking speed sensors, wiring, and connectors for any corrosion or damage.

In conclusion, the Chevrolet Code P1391 should not be taken lightly. Addressing this code quickly can not only improve your vehicle’s performance but also ensure your safety and that of others on the road.

Chrysler Code P1391 – Diagnosis and Solutions

The Chrysler fault code P1391 indicates a problem in the synchronization circuit between the crankshaft sensor (CKP) and the camshaft sensor (CMP). This fault, specific to Chrysler, Dodge, and Jeep vehicles, can disrupt engine timing, leading to irregular idling, jerking, or even engine failure. Here is a detailed analysis.

The synchronization between the crankshaft sensor and the camshaft sensor is crucial for the proper functioning of the engine. For example, a misalignment in this synchronization can lead to poor performance, excessive fuel consumption, and even long-term internal engine damage. Additionally, it is important to understand that modern vehicles heavily rely on electronic systems and sensors to optimize their performance. A failure in these systems can therefore have serious and costly consequences.

Importance of Synchronization

Proper synchronization not only ensures the engine runs correctly but is also essential for reducing polluting emissions. Modern engine management systems use information from these sensors to adjust combustion parameters in real time. Consequently, a fault in one of these sensors can compromise the overall efficiency of the vehicle.

Meaning of Code P1391

  • Description: “Intermittent Loss of CMP or CKP Sensor”.
  • Main Cause: The engine control module (ECU) detects an abnormal discrepancy between the signals from the two sensors during startup or while driving.
  • Consequences:
    • Incorrect fuel injection and ignition timing.
    • Risk of engine stalling or difficulty starting.

Common Symptoms

  1. Engine Shaking: Abnormal vibrations at idle or low RPM.
  2. Misfires: Hesitant acceleration and loss of power.
  3. Hard Starting: The engine cranks for a long time before starting.
  4. Engine Stalling: Sudden shutdown, especially when stopped.
  5. Check Engine Light Illuminated: Sometimes flashing in case of severe misfires.

Possible Causes

Other Associated Symptoms

In addition to the mentioned symptoms, a vehicle with code P1391 may also exhibit strange behaviors such as a knocking noise from the engine, a smell of unburned fuel, and higher than normal fuel consumption. These signs should be taken seriously as they may indicate more serious underlying problems.

  1. Electrical Problems:
    • Damaged wires or corroded connectors on the CKP/CMP sensors.
    • Short circuit or irregular voltage (e.g., blown fuse).
  2. Sensor Failures:
    • Faulty camshaft sensor (CMP) or crankshaft sensor (CKP).
    • Accumulation of metal debris on the sensors (magnetization).
  3. Mechanical Problems:
    • Loose or misaligned timing belt.
    • Damage to the distributor rotor (on equipped engines).
  4. PCM Module Faults: Rare, but possible (e.g., software error).

Diagnostic Procedure

  1. OBD-II Scanner:
    • Read associated fault codes (e.g., P0340/P0335 confirming a sensor problem).
    • Check live data: compare CKP/CMP signals.
  2. Visual Inspection:
    • Check sensor cables and connectors (look for cracks, corrosion).
    • Clean sensors (metal debris).
  3. Electrical Tests:
    • Measure sensor resistance (CKP: 200–1000 Ω; CMP: 150–900 Ω).
    • Test supply voltage (generally 5V or 12V).
  4. Mechanical Check:
    • Inspect the timing belt and pulleys (alignment, wear).

Recommended Repairs

  1. Replace Faulty Sensors:
    • Average cost: €70–150 (part + labor).
    • Prefer OEM parts (Mopar).
  2. Repair Wiring:
    • Replace damaged wires and clean connectors.
  3. Adjust Timing:
    • If the belt is loose: replace the belt and realign the pulleys.
  4. Update PCM:
    • If the problem persists, reprogram the ECU at a dealership.

Common Mistakes to Avoid

  • Ignoring the Timing Belt: Misalignment often simulates a sensor fault.
  • Neglecting Wiring: 80% of P1391 codes come from faulty electrical circuits, not the sensors themselves.
  • Forgetting the Basics: Always check battery voltage (a weak battery distorts signals).

Prevention and Maintenance

Regular maintenance of your vehicle is key to avoiding problems such as code P1391. Make sure to check connectors and cables during each service. Additionally, regular cleaning of the sensors can help maintain their efficiency. It is also recommended to regularly change the fuel filter to prevent the accumulation of debris that could harm the sensors.

Estimated Costs

Intervention Price (parts + labor)
CMP/CKP Sensor Replacement €100–250
Wiring Repair €80–150
Timing Belt Replacement €400–700

Conclusion

It is also vital to note that faulty sensors can sometimes be caused by other mechanical problems. For example, a faulty head gasket can lead to engine overheating, which could damage the sensors. Furthermore, the quality of the fuel used can also influence the proper functioning of the sensors. Using poor quality fuel can lead to a buildup of deposits that affects engine performance.

The Chrysler P1391 code points to a critical desynchronization between the engine position sensors. Although it can sometimes be resolved by simple cleaning or realignment, a thorough diagnosis is essential to avoid costly repairs. If you lack experience, consult a specialized Chrysler mechanic – delayed intervention can damage the catalytic converter or the engine.

Consequences of Non-Diagnosis

Failing to resolve a P1391 code can lead to serious consequences. An engine out of synchronization can suffer premature wear, which can cause costly repairs. Moreover, ignoring this problem can also lead to other fault codes that would further complicate diagnosis and repair. Therefore, it is crucial to act quickly at the first signs of failure.

Final Conclusion

In summary, the Chrysler P1391 code is a key indicator of potential problems in the engine synchronization system. Paying special attention to this code and performing proper diagnosis can save your engine from irreparable damage. If you are faced with this issue, do not hesitate to consult a professional to ensure the longevity of your vehicle.

P1391 Dodge Code: Diagnosis & Solutions

(Crankshaft/Camshaft Sensor Synchronization Issue)

The synchronization between the crankshaft sensor and the camshaft is essential for the proper functioning of the engine. If these sensors do not work correctly, it can lead to poor performance and even potential engine damage.

It is crucial to understand the implications of an error code like the Dodge Code P1391, as it can affect various aspects of vehicle driving and maintenance.

The error code Dodge Code P1391 is often associated with this problem.

When reported, the Dodge Code P1391 can also suggest that there is an underlying issue that requires immediate attention to avoid higher repair costs in the long term.

During diagnosis, the Dodge Code P1391 must be taken into account.

Meaning of Dodge Code P1391

This error code is an indicator of potential problems that can affect the overall operation of your vehicle. Understanding the meaning of this code is vital for proper diagnosis.

It is important to note that intermittent signal loss can also be caused by issues with the connectors, or even failures due to normal component wear.

  • This code may indicate a synchronization problem, such as the Dodge Code P1391.
  • It is recommended to check the Dodge Code P1391 when analyzing symptoms.
    • Fault: Intermittent loss of signal between the crankshaft sensor (CKP) and the camshaft sensor (CMP).
    • Consequence: The Powertrain Control Module (PCM) cannot synchronize injection and ignition → Risk of stalling, hard starting.
    • Affected Models:
      • Dodge Grand Caravan, Durango, Ram
      • Charger, Challenger (V6/V8 HEMI)
      • Journey, Nitro

    Common Symptoms

    Symptom Severity
    Engine shaking at idle ⚠️ Urgent
    Misfires during acceleration ⚠️ Urgent
    Check engine light on (or flashing) ⚠️🔧 Immediate Check
    Sudden engine shutdown 🛑 STOP (risk of breakdown)

    These vehicles may encounter various other technical issues that can also contribute to the recurrence of the Dodge Code P1391. Regular maintenance is therefore advised to prevent these problems.

    If you experience any of these symptoms, it is recommended to have your vehicle checked by a professional as soon as possible. Ignoring these signs can lead to more serious damage.

    Main Causes

    Studies show that sensor problems can also be aggravated by extreme weather conditions, making maintenance even more crucial.

    1. Electrical Problems (70% of cases):
      • Cut/chewed wires near the sensors (often exposed to heat).
      • Oxidized or loose connectors (CKP/CMP).
      • Blown fuse (check the under-hood fuse box).
    2. Sensor Failure:
      • Dead CKP or CMP (test resistance: CKP 200–1000Ω / CMP 150–900Ω).
      • Metal buildup on the sensor (magnetized by debris).
    3. Mechanical Problems:
      • Improperly tensioned/misaligned timing belt (on belt-driven engines).
      • Damaged crankshaft reluctor wheel.

    Quick Diagnosis (Key Steps)

    1. OBD2 Scanner:
      • Check for associated codes (e.g., P0340 = CMP / P0335 = CKP).
      • Observe live signals: the CMP should synchronize after 2 crankshaft revolutions.
    2. Physical Inspection:
      • Locate the sensors:
        CKP: Near the flywheel (transmission side).
        CMP: On the cylinder head (rear or front of the engine).
      • Check cables and connectors (disconnect the battery first!).
    3. Electrical Test:
      • Supply voltage: 5V or 12V (refer to workshop manual).
      • Resistance out of circuit (disconnect the connector).

    Effective Repairs

    Solution Estimated Cost (€)
    Replace CMP or CKP sensor 70–150 € (part)
    Repair damaged wiring harness 50–120 €
    Clean metal debris Free (compressed air)
    Replace timing belt 400–700 €
    Reprogram PCM 100–200 € (dealership)

    Typical Dodge Case: On *Grand Caravan 3.3L/3.8L*, an oxidized CMP connector under the air intake often triggers the P1391.

    Mistakes to Avoid

    • Ignoring the timing belt: A misaligned timing system will reactivate the code.
    • Forgetting the battery: Low voltage (<12V) distorts signals → Test it first!
    • Neglecting connectors: Clean them with contact cleaner before replacing a sensor.

    Emergency & Tips

    • If the engine stalls or the light flashes: Stop the vehicle → Risk of catalytic converter damage.
    • Temporary solution: Turn off/restart the engine (the PCM may resynchronize the sensors).

    ℹ️ Technical Reference: Specific procedure in the Dodge DSMS/DealerCONNECT manual for your model. If the code returns after repair, check the ASD Relay (Automatic Shutdown Relay).

    Understanding these symptoms will help you better anticipate and react to problems that may arise with your vehicle, especially in the case of the Dodge Code P1391.

    Effective repairs also involve systematically checking related parts, as simply replacing a faulty part may not be enough to solve the underlying problem.

    It is essential to conduct a thorough analysis of each symptom to identify the real causes of the problems and avoid unnecessary repairs.

    Finally, if the Dodge Code P1391 persists after repairs, consult a qualified technician for a more in-depth evaluation and to ensure all potential causes have been addressed.

    Ford fault code P1391

    Ford Fault Code P1391: CKP/CMP Timing Problem

    (Loss of CMP or CKP Signal Intermittent)

    When the CMP or CKP sensor fails, it can also cause abnormal engine vibrations, poor acceleration performance, and even difficulty shifting certain gears. These symptoms may occur when driving uphill or during rapid acceleration.

    The Ford fault code P1391 indicates a timing problem between the crankshaft sensor and the camshaft sensor.

    This error code is often an early indicator of more serious engine-related problems, meaning it is essential not to ignore the Ford fault code P1391. For example, if this code appears, it may be wise to check the crankshaft and camshaft position sensors, as their failure can lead to a loss of engine performance.

    Technical Meaning

    • Fault: The PCM detects an intermittent loss of synchronization between:
      • CKP (Crankshaft Position Sensor): Crankshaft sensor.
      • CMP (Camshaft Position Sensor): Camshaft sensor (called PIP Profile Ignition Pickup on some models).
    • Impact: Engine timing error → Desynchronized injection/ignition → Risk of stalling and misfires.

    Affected Ford Models

    Model Common Engines
    Ford Focus (2000-2011) 2.0L Duratec, Zetec
    Ford Escape (2001-2012) 2.3L, 3.0L V6
    Ford Explorer (2002-2010) 4.0L V6, 5.0L V8
    Ford Fiesta (2004-2019) 1.6L Ti-VCT
    Ford Fusion (2006-2012) 2.5L, 3.0L V6

    Common Symptoms

    • 🔥 Engine stalling at idle (red lights, traffic jams).
    • ⚠️ Hard starting (cranks for 5-10 seconds before starting).
    • 🛑 Ignition misfires under load (uphill driving, acceleration).
    • 💡 Check engine light on (sometimes flashing in case of severe misfires).
    • 📉 Unstable idle (steering wheel/dashboard vibrations).

    Specific Causes in Ford

    1. Electrical Failures (60-70% of cases):
      • Chafed/burned wires near the exhaust manifold (especially Focus/Fiesta).
      • CMP connector flooded in rain (low location on engine block).
      • Corrosion in the CKP connector (proximity to road/moisture).
    2. Mechanical Problems:
      • Damaged CKP reluctor wheel (broken teeth, rust on old engines).
      • Excessive camshaft gear play (models with timing chain).
    3. Other Triggers:
      • Faulty PCM (rare, but documented on Escape 2005-2008).
      • Dirty engine oil: Clogs the CMP sensor (especially on 4.0L Explorer).

    Step-by-Step Diagnosis

    1. Advanced OBD2 Scan:
      • Check associated codes: P0340 (CMP), P0335 (CKP), P0016 (desynchronization).
      • Analyze live signals: The CKP:CMP ratio must be 2:1 (2 crankshaft revolutions = 1 camshaft revolution).
    2. Physical Inspection:
      • Sensor locations:
        CKP: Flywheel (transmission side).
        CMP: Cylinder head (timing side) – Caution: Often buried under cables.
      • Visual test: Exposed wires, corroded connectors.
    3. Electrical Tests:SensorSupply VoltageResistance (Ω)CKP5V or 12V200–1,000CMP5V (8V on PIP)150–900Use a multimeter: Measure out of circuit.

    Recommended Repairs

    Solution Cost (€) Urgency
    Replace CMP sensor (Focus/Fiesta) 40–100 € 🔧🔧
    Repair CKP harness (chafed) 50–150 € 🔧
    Clean CKP reluctor wheel 0 € (compressed air) 🔧
    Replace CMP seal (oil leak) 20–80 € 🔧🔧
    Reprogram PCM (dealer) 100–250 € ⚠️

    Concrete example: On the Ford Focus 2.0L, the CMP is located under the ignition module → Disassembly required. An oxidized connector there systematically triggers P1391.

    For a more in-depth diagnosis, it is highly recommended to use an OBD-II scanner to read not only the P1391 code but also other codes that may be present. This can help identify if the problem comes from other components of the ignition or injection system.

    Common Mistakes to Avoid

    • ❌ Replacing the CKP without checking the wiring: Wires often chafe against the block on Focus models.
    • ❌ Forgetting the CMP seal: An oil leak floods the sensor → New failure within 3 months.
    • ❌ Ignoring code P0016: Indicates a mechanical problem (timing, chain) requiring major intervention.

    Other factors specific to the Ford brand can also contribute to the appearance of the Ford fault code P1391. For example, older Focus and Fiesta models are particularly vulnerable to chafing wires due to natural wear or incorrect installation of other components under the hood.

    Ford Technical Tips

    1. Emergency restart: If the engine stalls, turn the ignition off/on → The PCM attempts a resynchronization.
    2. Recommended tools: Forscan scanner (Ford compatible) to access detailed PCM data.
    3. Check the PCM relay: On Escape/Fusion, a faulty relay cuts power to the sensors.

    ⚠️ Warning: An untreated P1391 can damage the catalytic converter (misfires → overheating). Consult a mechanic if symptoms persist after basic diagnosis.

    Source: Ford Workshop Manual (Motorcraft), TSG procedures 2023.

    It is also useful to check the sensor supply voltage with a multimeter, as abnormal voltages can signal broader electrical problems in the vehicle.

    Repairs can vary depending on the severity of the problem. Sometimes, a simple cleaning of the connectors may suffice, while other times, replacing the sensors or a more thorough examination of the wiring may be necessary to definitively resolve the Ford fault code P1391.

    In conclusion, correctly handling error codes like the Ford fault code P1391 is essential to maintaining your vehicle’s performance and safety. By quickly identifying and addressing problems, you can avoid costly repairs in the future.