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
- 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).
- Mechanical Problems:
- Damaged CKP reluctor wheel (broken teeth, rust on old engines).
- Excessive camshaft gear play (models with timing chain).
- 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
- 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).
- Physical Inspection:
- Sensor locations:
CKP: Flywheel (transmission side).
CMP: Cylinder head (timing side) – Caution: Often buried under cables. - Visual test: Exposed wires, corroded connectors.
- Sensor locations:
- 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
- Emergency restart: If the engine stalls, turn the ignition off/on → The PCM attempts a resynchronization.
- Recommended tools: Forscan scanner (Ford compatible) to access detailed PCM data.
- 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.