P0338 High Input in Crankshaft Position Sensor A Circuit

What does it mean?

This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to vehicles equipped with OBD-II (Jeep, Nissan, Dodge, Ram, BMW, Ford, GM, etc.). Although generic, specific repair steps may vary by make/model.

In the past, when I diagnosed a stored P0338 code, it was due to the powertrain control module (PCM) detecting a high input voltage signal from the crankshaft position sensor (CKP).

CKP sensors monitor engine speed (RPM) and crankshaft position. The crankshaft position is used by the PCM to calculate ignition spark timing. Camshafts rotate at half the speed of the crankshaft, so it is important that the PCM is able to distinguish between the engine’s intake and exhaust strokes (rotations). The CKP sensor and each camshaft position sensor (CMP) have one or more dedicated circuits to provide the PCM with an input signal, a 5-volt reference signal, and a ground.

CKP sensors are typically Hall effect electromagnetic types and are mounted externally on the engine. They are placed in very close proximity (usually only a few thousandths of an inch) to a circuit completing the engine ground. This engine ground is typically a reluctor ring (with precision-machined teeth) attached to either end of the crankshaft or integrated into the crankshaft itself. Systems with multiple CMP sensors may use a reluctor ring at one end of the crankshaft and another machined at the center of the crankshaft.

Typically, the CKP sensor is mounted so that the crankshaft’s reluctor ring passes within a few thousandths of an inch of its magnetic tip. As the crankshaft rotates, the raised areas of the reluctor ring complete an electromagnetic circuit with the sensor. The indentations (between the raised areas) briefly interrupt the circuit. The PCM perceives these rapid circuit completions and interruptions as a waveform pattern representing voltage fluctuations.

The PCM continuously compares the input signals from the crankshaft position and camshaft position sensor circuits. If the CKP input voltage is too high over a defined period of time, a P0338 code will be stored and a MIL may be illuminated.

Other crankshaft position sensor fault codes include P0335, P0336, P0337, and P0339.

Code Severity and Symptoms

When a P0338 is stored, a no-start condition will likely accompany it. For this reason, this code should be classified as severe. If the engine starts and runs, the risk of a no-start remains high in the near future.

Symptoms of this code may include:

Engine does not start
The tachometer (if applicable) does not register RPM when the engine is cranked
Hesitation during acceleration
Poor engine performance
Reduced fuel efficiency

Causes

Possible causes for this code being set are as follows:

Faulty CKP sensor
Open or shorted wiring to the CKP sensor
Corroded or fluid-soaked connector at the CKP sensor
PCM programming error or faulty PCM
Alternator overcharging and affecting PCM operation

Diagnostic and Repair Procedures

Access to a suitable diagnostic scanner, with a built-in digital volt/ohmmeter (DVOM) and an oscilloscope, will be necessary before diagnosing a P0338 code. As a reliable source for vehicle information, I will also need access to All Data DIY.

The most successful code diagnostics start with a visual inspection of all wiring harnesses and connectors related to the system. Petroleum-based fluids can compromise the protective insulation of wiring and lead to short circuits or open circuits (and a stored P0338), so circuits, electrical sensors, and/or connectors that have been contaminated by engine oil, coolant, or power steering fluid should be carefully inspected.

Connect the scanner to the vehicle’s diagnostic port to retrieve stored fault codes and freeze frame data. Note this information as it will help if the P0338 proves to be intermittent. Test drive the vehicle (if possible) to see if the code resets. If it does:

Locate a system wiring diagram from the vehicle information source and check the voltage at the CKP sensor. Typically, a five-volt reference is used for CKP sensor operation, but check the manufacturer’s specifications for the vehicle in question. A ground signal and one or more output circuits should also be present. Proceed to the next step if reference voltage and ground signals are detected at the CKP sensor connector.

Using the DVOM, disconnect the electrical connector of the CKP sensor in question and test it according to the manufacturer’s specifications. Replace the CKP sensor if the resistance levels do not meet the manufacturer’s specifications. If the CKP sensor resistance values match the manufacturer’s specifications, proceed to the next step.

After reconnecting the CKP sensor in question, attach the oscilloscope’s positive test lead to the signal output wire and connect the negative lead to the CKP sensor’s ground circuit. Power on the oscilloscope and select the operating voltage setting. Start the engine and observe the waveform pattern on the oscilloscope. Focus on unexpected spikes or glitches. If spikes or glitches are detected, carefully wiggle the wiring harness and connector of the CKP sensor in question to determine if the issue is a loose connection or a faulty sensor. If there is a broken or worn reluctor ring, or if the magnetic tip of the CKP sensor has excessive metal debris attached, it can cause missing voltage blocks in the waveform pattern. Proceed to the next step if no issues are found in the waveform pattern.

Locate the PCM connector, insert the oscilloscope test leads into the CKP sensor input signal and ground circuits, and observe the waveform pattern. Suspect an open or shorted circuit between the CKP sensor connector and the PCM connector if the waveform pattern near the PCM connector is different from what was seen when the test leads were connected near the CKP sensor. If this is the case, disconnect all associated controllers and test the individual circuits with the DVOM. Shorted or open circuits will need to be repaired or replaced. You may have a faulty PCM or a PCM programming error if the waveform pattern is identical to what was seen when the test leads were connected near the CKP sensor.

Additional Diagnostic Notes:

Some manufacturers recommend replacing CKP and CMP sensors as a set
Use technical service bulletins to aid the diagnostic process

P0339 Intermittent Crankshaft Position Sensor B Circuit

What does it mean?

This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to OBD-II equipped vehicles (Chevy, Ford, BMW, Dodge, GMC, Kia, Hyundai, Honda, Toyota, etc.). Although generic, the specific repair steps may vary by make/model.

If your vehicle has a stored P0339 code, it means the Powertrain Control Module (PCM) has detected an intermittent or erratic voltage signal from the secondary crankshaft position sensor (CKP). When an OBD II system uses multiple CKP sensors, the B sensor typically refers to a secondary CKP sensor.

Engine speed (RPM) and crankshaft position are monitored using the CKP sensor. The PCM calculates ignition spark timing using the crankshaft position. When you consider that camshafts rotate at half the speed of the crankshaft, you see why it’s so important for the PCM to distinguish between the engine’s intake and exhaust strokes (rotations). The CKP sensor circuit includes one or more dedicated circuits to provide the PCM with an input signal, a 5-volt reference signal, and a ground.

CKP sensors are most often of the Hall effect electromagnetic variety. They are typically mounted on the outside of the engine and placed in very close proximity (usually only several thousandths of an inch) to a circuit completing the engine ground. The engine ground is usually a reluctor ring (with precision-machined teeth) attached to one end of the crankshaft or integrated into the crankshaft itself. Some systems with multiple CKP sensors may use a reluctor ring at one end of the crankshaft and another machined at the center of the crankshaft. Others will simply mount sensors in multiple positions around a reluctor ring.

The CKP sensor is mounted so the reluctor ring passes within a few thousandths of an inch of its magnetic tip when the crankshaft rotates. The raised areas (teeth) of the reluctor ring complete an electromagnetic circuit with the sensor and the indentations between the raised areas briefly interrupt the circuit. The PCM recognizes these continuous circuit completions and interruptions as a waveform pattern representing voltage fluctuations.

Input signals from CKP sensors are continuously monitored by the PCM. If the input voltage from the crankshaft position sensor is too low over a defined period of time, a P0339 code will be stored and an MIL may be illuminated.

Other B crankshaft position sensor fault codes include P0335, P0336, P0337, and P0338.
Code Severity and Symptoms

A no-start condition will likely accompany a stored P0339 code. Therefore, this code could be classified as severe.

Symptoms of this code may include:

Engine does not start
Tachometer (if applicable) does not register RPM when engine is cranked
Hesitation during acceleration
Poor engine performance
Reduced fuel efficiency

Causes

Possible causes for setting this code are:

Faulty CKP sensor
Open or shorted wiring to the CKP sensor
Corroded or fluid-soaked connector at the CKP sensor
PCM programming error or faulty PCM

Diagnostic and Repair Procedures

I would need a diagnostic scanner, with a built-in digital volt/ohmmeter (DVOM) and an oscilloscope, before diagnosing a P0339 code. A reliable source of vehicle information, such as All Data DIY, will also be required.

A visual inspection of all wiring harnesses and connectors related to the system is a good place to start your diagnosis. Circuits that have been contaminated by engine oil, coolant, or power steering fluid should be carefully inspected as petroleum-based fluids can compromise the protective insulation on wiring and lead to short circuits or open circuits (and a stored P0339).

If the visual inspection yields no results, connect the scanner to the vehicle’s diagnostic port and retrieve all stored fault codes and freeze frame data. Writing down this information may prove useful if the P0339 proves to be intermittent. If possible, test drive the vehicle to see if the code resets.

If the P0339 resets, find a wiring diagram of the system from your vehicle information source and check the voltage at the CKP sensor. A five-volt reference is normally used for CKP sensor operation but check the manufacturer’s specifications for the vehicle in question. One or more output circuits and a ground signal will also be present. If the reference voltage and ground signals are detected at the CKP sensor connector, proceed to the next step.

Using the DVOM, test the CKP sensor in question according to the manufacturer’s recommendations. If the CKP sensor’s resistance levels do not meet the manufacturer’s recommendations, suspect it is faulty. If the CKP sensor’s resistance matches the manufacturer’s specifications, proceed to the next step.

Attach the oscilloscope’s positive test lead to the signal output wire and connect the negative lead to the CKP sensor’s ground circuit after reconnecting the CKP sensor in question. Choose the appropriate voltage setting on the oscilloscope and turn it on. Observe the waveform pattern on the oscilloscope with the engine idling in park or neutral. Monitor for voltage spikes or glitches in the waveform pattern. If abnormalities are detected, test the wiring harness and connector (for the CKP sensor) to determine if the issue is a loose connection or a faulty sensor. If the CKP sensor’s magnetic tip contains excessive metal debris or if there is a broken or worn reluctor ring, this can cause missing voltage blocks in the waveform pattern. Proceed to the next step if no issues are found in the waveform pattern.

Locate the PCM connector and insert the oscilloscope test leads into the CKP sensor input signals and ground circuits, respectively. Observe the waveform pattern. If the waveform pattern near the PCM connector is different from what was seen when the test leads were connected near the CKP sensor, suspect an open or shorted circuit between the CKP sensor connector and the PCM connector. If this is true, disconnect all associated controllers and test the individual circuits with the DVOM. You will need to repair or replace shorted or open circuits. The PCM may be faulty, or you may have a PCM programming error, if the waveform pattern is identical to what was seen when the test leads were connected near the CKP sensor.

Additional Diagnostic Notes:

Some manufacturers recommend replacing CKP and CMP sensors as a set
Use technical service bulletins to assist in the diagnostic process

Knock Sensor 4 Circuit (Bank 2)

Meaning of Code P033A

Code P033A is a generic OBD-II code related to the powertrain. It indicates that the engine control module (ECM) has detected an abnormal reading from the knock sensor #4 on bank 2 (the side of the engine that does not contain cylinder #1). This sensor monitors abnormal vibrations (knocking) that could damage the engine.

How the Knock Sensor Works

  • Technology: Piezoelectric sensor generating voltage in response to vibrations.
  • Location: Typically screwed into the engine block, often near coolant passages.
  • Risk: Removing the sensor on a hot engine can cause burns (pressurized coolant).

Severity of Code P033A

This code is critical as it may indicate:

  • Internal engine failure (e.g., damaged connecting rod).
  • Risk of permanent damage if ignored.

Common Symptoms

  • Check engine light on.
  • Hesitation or loss of power during acceleration.
  • Abnormal metallic noises (knocking) from the engine.
  • Increased fuel consumption.

Possible Causes

  1. Mechanical Issues:
    • Repeated misfires.
    • Internal damage (e.g., worn connecting rod bearings).
  2. Electrical Failures:
    • Faulty knock sensor.
    • Damaged wiring or corroded connectors.
  3. Other Causes:
    • Poor quality or contaminated fuel.
    • ECM programming error.

Diagnostic Procedures

  1. Visual Inspection:
    • Check the sensor wiring and connectors (corrosion, cuts).
    • Look for signs of physical damage (e.g., cracked sensor).
  2. Using an OBD-II Scanner:
    • Read stored codes and real-time sensor data.
    • Compare sensor voltage to manufacturer specifications.
  3. Sensor Testing:
    • Measure resistance and voltage with a multimeter.
    • Replace the sensor if values are out of range.

Important Precautions

  • Engine Cooling: Wait 2-3 hours before removing the sensor to avoid burns.
  • Technical Reference: Consult a model-specific repair manual to accurately locate sensor #4.

Recommended Solutions

  1. Replace the Faulty Sensor:
    • Use an appropriate wrench to avoid damaging the threads.
    • Apply anti-leak sealant if necessary.
  2. Repair the Wiring:
    • Reinstall or replace damaged wires.
    • Clean connectors with contact spray.
  3. Diagnose Mechanical Issues:
    • Check cylinder compression.
    • Analyze engine oil for metal particles.
  4. Update the ECM:
    • Consult a professional for reprogramming if needed.

Estimated Costs

  • Knock Sensor: €50 to €150 (depending on the model).
  • Labor: 1 to 2 hours of work (€80 to €200).

Conclusion

Code P033A should not be ignored, as it may reveal serious issues (e.g., engine damage). Prompt action, combined with accurate diagnostic tools, will prevent costly repairs. If in doubt, consult a certified mechanic for a thorough diagnosis.

P033B Knock Sensor 4 Circuit Voltage, Bank 2

What does it mean?

This diagnostic code (DTC) is a generic powertrain code, meaning it applies to vehicles equipped with OBD-II. Although generic, specific repair steps may vary by brand/model.

Knock sensors are used to detect engine pre-detonation (engine knocking or pinging). The knock sensor (KS) is typically a two-wire sensor. A 5-volt reference is provided to the sensor, and there is a signal return from the knock sensor to the PCM (Powertrain Control Module). For this DTC, it refers to knock sensor #4 on bank 2; refer to the vehicle-specific service manual for the specific location. Bank 2 is always the side of the engine that does not contain cylinder #1.

The sensor’s signal wire informs the PCM when a knock occurs and to what degree of severity. The PCM will retard the spark timing to prevent pre-detonation. Most PCMs have the ability to learn spark knock trends in the engine during normal operation.

If the PCM determines that the knock is out of the ordinary or the noise level is abnormally high, P033B may be set. If the PCM detects that the knock is severe and cannot be eliminated by retarding the spark timing, P033B may set. Keep in mind that knock sensors cannot distinguish between pre-detonation knock and engine mechanical problem noises.

Symptoms

Symptoms of a P033B DTC may include:

    MIL (Malfunction Indicator Lamp) illumination
    Audible knocks from the engine compartment
    Engine pinging under acceleration

Causes

Potential causes of a P033B code include:

    Knock sensor circuit shorted to voltage
    Knock sensor has failed
    Knock sensor connector is damaged
    Knock sensor circuit open or shorted to ground
    Moisture in the knock sensor connectors
    Incorrect fuel octane
    PCM has failed

Possible Solutions

If engine knocking is audible, first correct the source of the mechanical problem, then retest. Ensure the correct fuel octane has been used in the engine. Using fuel with a lower octane rating than specified can cause knocking or detonation and may trigger P033B.

Disconnect the knock sensor and check for water or corrosion in the connector. If the knock sensor has a seal, check that no engine block coolant is fouling the sensor. Repair if necessary.

Turn the ignition to the ON position with the engine off. Ensure 5 volts are present at the KS #4 connector. If so, check the proper resistance between the KS terminal and engine ground. You will need a vehicle specification for this. If the resistance is out of specifications, replace the knock sensor. If the resistance is normal, reconnect the KS and start the engine at idle. Using a scan tool in the data stream, observe the KS value. Does it indicate that a knock is present at idle? If so, replace the knock sensor. If the knock sensor shows no knocking at idle, tap on the engine block while observing the knock signal. If it does not show a signal corresponding to the taps, replace the knock sensor. If it does, check that the knock sensor wiring is not routed next to ignition wires. If there were no 5 volts present at the knock sensor connector when it was disconnected with KOEO (Key On Engine Off), go back to the PCM connector. Turn off the ignition and cut the 5-volt knock sensor reference wire in an easy-to-repair location (or remove the wire from the PCM connector). With KOEO, check for 5 volts from the PCM side of the cut wire. If 5 volts is not present, suspect a faulty PCM. If 5 volts is present, repair the short in the 5-volt reference circuit.

Since the reference circuit is a shared circuit, you will need to check all engine sensors that receive a 5-volt reference. Disconnect each sensor one by one until the reference voltage returns. When it returns, the last sensor you disconnected is the shorted sensor. If no sensor is shorted, check that the wiring harness is not shorted on the reference circuit.

P033C Knock Sensor 4 Circuit Low (Bank 2)

What does it mean?

This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to vehicles equipped with OBD-II (Dodge, Ram, Ford, GMC, Chevrolet, VW, Toyota, etc.). Although generic, specific repair steps may vary by make/model.

A P033C fault code means the Powertrain Control Module (PCM) has detected a lower than expected sensor reading from the #4 knock sensor on bank 2. Bank 2 is always the engine cylinder bank that does not contain cylinder #1. Refer to a vehicle-specific repair source to determine which sensor is the #4 knock sensor.

Typically threaded directly into the engine block, the knock sensor is a piezoelectric sensor. The location of sensors in a multi-sensor system may vary by manufacturer, but most are located on the sides of the block (between the cylinder liner freeze plugs). Knock sensors located on the sides of the engine block are often screwed directly into the engine coolant passages. When the engine is hot and the engine cooling system is pressurized, removing these sensors can result in severe burns from hot coolant. Before removing a knock sensor, allow the engine to cool and always dispose of coolant properly.

A piezoelectric sensing crystal is at the heart of the knock sensor. When shaken or vibrated, the piezoelectric crystal produces a small amount of voltage. Since the knock sensor control circuit is normally a single-wire ground circuit, the voltage generated by vibration is recognized by the PCM as engine noise or vibration. The severity of the vibration encountered by the piezoelectric crystal (inside the knock sensor) determines the voltage level produced in the circuit.

If the PCM detects a degree of voltage from the knock sensor indicating spark knock; it may retard ignition timing and no knock sensor control code may be recorded. If the PCM detects a voltage level from the knock sensor that indicates more severe engine noise (such as a connecting rod contacting the inside of the engine block), it may interrupt fuel delivery and ignition spark to the affected cylinder and a knock sensor code will be stored.

Code Severity and Symptoms

A stored P033C code should be considered severe as it could indicate internal engine failure.

Symptoms of this code may include:

Hesitation during acceleration
Below normal engine performance
Abnormal noises from the engine area
Increased fuel consumption

Causes

Possible causes for this code being set are:

Ignition misfires
Faulty knock sensor
Internal engine problem
Use of contaminated or low-quality fuel
Faulty knock sensor control wiring and/or connectors
Incorrect PCM or PCM programming error

Diagnostic and Repair Procedures

To diagnose a P033C code, a diagnostic scanner, a digital volt/ohmmeter (DVOM), and a reliable vehicle-specific repair resource will be needed. If the engine seems to be knocking or excessively noisy, address this issue before attempting diagnosis for any knock sensor code.

Check Technical Service Bulletins (TSBs) that may apply to your year/make/model. If the problem is known, there may be a bulletin providing specific diagnostic and repair assistance for your exact issue. This can save you time and money.

Start with a visual inspection of all wiring harnesses and connectors related to the system. Look for corroded, burned, or otherwise damaged wires and connectors that could create an open or short circuit. Knock sensors are often located in the lower part of the engine block. This makes them susceptible to damage when heavy parts (like starters and motor mounts) are replaced. System connectors, wiring, and fragile knock sensors are frequently broken during nearby repairs.

Connect the OBD-II scanner to the vehicle’s diagnostic connector and retrieve all stored diagnostic trouble codes and freeze frame data. Note this information for use in the diagnostic process. Clear the codes and test-drive the vehicle to see if they reset.

If the P033C resets, start the engine and use the scanner to observe the knock sensor data. If the scanner indicates that the knock sensor voltage is not within manufacturer specifications, use the DVOM to test the live data at the knock sensor connector. If the signal at the connector is within specifications, suspect a wiring problem between the sensor and the PCM. If the voltage at the knock sensor connector is not within specifications, suspect a faulty knock sensor. If replacing the sensor is the next step, ensure you do not come into contact with hot coolant. Wait for the engine to cool before removing the old sensor.

P033D Knock Sensor 4, High Circuit (Bank 2)

What does it mean?

This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to OBD-II equipped vehicles. Although generic, specific repair steps may vary by make/model.

Knock sensors are used to detect engine pre-detonation (engine knock or ping). The knock sensor (KS) is typically a two-wire sensor. A 5-volt reference is provided to the sensor and there is a signal return from the knock sensor to the PCM (Powertrain Control Module).

The sensor’s signal wire informs the PCM when a knock occurs and to what degree of severity. The PCM will retard spark timing to prevent pre-detonation. Most PCMs have the capability to learn spark knock trends in the engine during normal operation.

If the PCM determines that the knock is out of the ordinary or that the noise level is abnormally high for knock sensor #4 on bank 2, P033D may set. If the PCM detects that the knock is severe and cannot be eliminated by retarding spark timing, P033D may set. Keep in mind that knock sensors cannot distinguish between pre-detonation knock and engine mechanical problem noises. Bank 2 is always the engine side that does not contain cylinder #1. Refer to a vehicle-specific repair guide to determine the location of sensor #4 on your particular vehicle.

Symptoms

Symptoms of a P033D DTC may include:

    MIL (Malfunction Indicator Lamp) illumination
    Audible knocking from the engine compartment
    Engine ping during acceleration

Causes

Potential causes of a P033D code include:

    Damaged knock sensor connector
    Knock sensor circuit open or shorted to ground
    Knock sensor circuit shorted to voltage
    Failed knock sensor
    Moisture in knock sensor connectors
    Incorrect fuel octane
    Failed PCM

Possible solutions

If engine knocking is audible, first correct the source of the mechanical problem, then retest. Ensure the correct fuel octane has been used in the engine. Using fuel with a lower octane rating than specified can cause knocking or detonation and may trigger P033D.

Disconnect the knock sensor and check for water or corrosion in the connector. If the knock sensor has a seal, check that no engine block coolant is fouling the sensor. Repair as necessary.

Turn the ignition to the ON position with the engine off. Verify that 5 Volts are present at the KS connector. If so, check the proper resistance between the KS terminal and engine ground. You will need a vehicle specification for this. If the resistance is out of specifications, replace the knock sensor. If the resistance is normal, reconnect the KS and start the engine at idle. Using a scan tool in the data stream, observe the KS value. Does it indicate that knocking is present at idle? If so, replace the knock sensor. If the knock sensor shows no knocking at idle, tap on the engine block while observing the knock signal. If it does not show a signal corresponding to the taps, replace the knock sensor. If it does, check that the knock sensor wiring is not routed next to ignition wires. If there was no 5 volts present at the knock sensor connector when it was disconnected with KOEO (Key On Engine Off), go back to the PCM connector. Turn off the ignition and cut the 5-volt knock sensor reference wire in an easily repairable location (or remove the wire from the PCM connector). With KOEO, check for 5 volts from the PCM side of the cut wire. If 5 volts is not present, suspect a faulty PCM. If 5 volts are present, repair the short circuit in the 5-volt reference circuit.

Since the reference circuit is a shared circuit, you will need to check all engine sensors that receive a 5-volt reference. Disconnect each sensor one by one until the reference voltage returns. When it returns, the last sensor you disconnected is the shorted sensor. If no sensor is shorted, check that the wiring harness is not shorted on the reference circuit.

P033E Knock Sensor 4 Circuit Intermittent (Bank 2)

What does it mean?

This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to OBD-II equipped vehicles (Dodge, Ram, Ford, GMC, Chevrolet, VW, Toyota, etc.). Although generic, the specific repair steps may vary by make/model.

In instances where I have been faced with diagnosing a stored P033E code, it has been indicative of the powertrain control module (PCM) detecting an intermittent knock sensor signal for engine bank two. The knock sensor 4 designation may refer to a particular sensor (in a multi-sensor setup) or it may point to a specific cylinder. Bank 2 refers to the engine bank that does not contain cylinder number one. Consult a reliable vehicle information source for the knock sensor system configuration for the vehicle in question.

Typically threaded directly into the engine block, the knock sensor is a piezoelectric sensor. The location of sensors in a multi-sensor system can vary by manufacturer, but most are located on the sides of the block (between the cylinder head coolant jacket freeze plugs). Knock sensors that are located on the sides of the engine block are often screwed directly into engine coolant passages. When the engine is hot and the engine cooling system is under pressure, removing these sensors can result in severe hot coolant burns. Before removing any knock sensor, allow the engine to cool and always dispose of coolant properly.

A piezoelectric sensing crystal is at the heart of the knock sensor. When shaken or vibrated, the piezoelectric crystal produces a small amount of voltage. Since the knock sensor control circuit is normally a one-wire ground circuit, the voltage generated by vibration is recognized by the PCM as engine noise or vibration. The severity of the vibration encountered by the piezoelectric crystal (inside the knock sensor) determines the level of voltage produced in the circuit.

If the PCM detects a degree of knock sensor voltage indicating spark knock; it may retard ignition timing and no knock sensor control code may be recorded. If the PCM detects a level of knock sensor voltage that indicates more severe engine noise (like a connecting rod contacting the inside of the engine block), it may interrupt fuel delivery and ignition spark to the affected cylinder and a knock sensor code will be stored.

A very small voltage is always produced by the knock sensor when the engine is running. This is because slight vibration is unavoidable, no matter how smoothly the engine is running. If the PCM detects an unexpected signal from knock sensor 4, such as battery voltage, complete battery ground, or pulsing voltage, a P033E code will be stored and a MIL may be illuminated.

Related knock sensor/circuit malfunction codes include P0324, P0325, P0326, P0327, P0328, P0329, P0330, P0331, P0332, P0333, and P0334.

Code Severity and Symptoms

A stored P033E code could be indicative of a severe internal engine failure. For this cause, it should be addressed with some urgency.

Symptoms of this code may include:

Decreased engine performance
Hesitation upon acceleration
Loud noises from the engine area
Decreased fuel efficiency

Causes

Possible causes for setting this code are as follows:

Faulty knock sensor
Internal engine malfunction
Misfire/s
Contaminated or poor quality fuel
Faulty knock sensor control wiring and/or connectors
Incorrect PCM or PCM programming error

Diagnostic and Repair Procedures

To diagnose a P033E code, a diagnostic scanner, digital volt/ohmmeter, and a reliable vehicle information source will be needed. If the engine feels like it is knocking or is excessively noisy, resolve this issue before attempting diagnosis for any knock sensor code.

Consult your vehicle information source for technical service bulletins (TSBs) that coincide with the symptom(s) displayed and the code(s) stored in the vehicle in question. If the issue you are experiencing is common; the correct TSB can help lead to a successful diagnosis. Follow the diagnostic steps in the TSB and you will likely arrive at the correct solution.

I like to start with a visual inspection of all wiring harnesses and connectors related to the system. I look for burned, corroded, or otherwise broken wires and connectors that may create an open or shorted circuit. Knock sensors are often located in the lower portion of the engine block. This makes them susceptible to damage when heavy components (like starters and motor mounts) are replaced. System connectors, wiring, and fragile knock sensors are frequently broken during nearby repairs.

Connect the scanner to the vehicle diagnostic connector and retrieve all stored codes and freeze frame data. Note this information for use in the diagnostic process. Clear the codes and test drive the vehicle to see if they reset.

If the P033E resets, start the engine and use the scanner to observe live knock sensor data. If the scanner indicates that the knock sensor voltage is not within manufacturer specifications, use the DVOM to test the live data at the knock sensor connector. If the signal at the connector is within specifications, suspect a wiring problem between the sensor and the PCM. If the voltage at the knock sensor connector is not within specifications, suspect a faulty knock sensor.

Additional Diagnostic Notes:

Multi-knock sensor systems are arranged differently from vehicle to vehicle. Be careful to address the correct knock sensor for the displayed code
Beware of hot, pressurized coolant when removing knock sensors that are threaded into engine coolant passages

P033F ISO/SAE Reserved

P011E, P011F ISO/SAE reserved

P0340 Camshaft Position Sensor Circuit Malfunction

What is the P0340 Code?

The P0340 code is a generic OBD-II code related to the powertrain. It indicates a problem in the Camshaft Position Sensor (CPS) circuit. Although it applies to most vehicles manufactured since 1996 (Toyota, Ford, Nissan, Honda, etc.), repair steps may vary by model.

Common Symptoms

  • Hard starting or complete failure to start.

  • Rough idling or engine stalling.

  • Loss of power during acceleration.

  • Illumination of the check engine light (⚠️).

Possible Causes

The issue may stem from:

  1. Electrical failure:

    • Damaged wires, short circuits, or corroded connectors.

    • Open circuit (signal interruption).

  2. Hardware problems:

    • Faulty camshaft position sensor (CPS).

    • Defective crankshaft sensor.

  3. PCM failure:

    • Faulty engine control module (rare case).

Diagnostic Procedure

  1. Visual inspection:

    • Check the CPS wiring and connectors (corrosion, exposed wires).

  2. Electrical tests:

    • Measure sensor voltage (typically 12V) and circuit continuity.

    • Compare values with manufacturer specifications.

  3. Sensor verification:

    • Test the CPS with a multimeter or oscilloscope (expected sine wave signal).

  4. Cross-diagnosis:

    • Check the crankshaft sensor, often related to the CPS.

Recommended Solutions

  • Replace the CPS if tests confirm its failure.

  • Repair the circuit: Replace damaged wires or connectors.

  • Reset the PCM after repair to clear the code.

  • Consult a professional if PCM issues are suspected.

Key Points to Remember

  • Do not automatically replace the CPS: 30% of cases are related to wiring.

  • Use an advanced diagnostic tool to analyze live data (e.g., cycle report, CPS signal).

  • On some models (e.g., Honda, Toyota), incorrect timing belt adjustment can trigger this code.

P0341 Camshaft Position Sensor Circuit Range/Performance

Meaning

The powertrain control module (PCM) has detected an anomaly in the camshaft position sensor (CPS) signal. This sensor transmits two critical pieces of information:

  1. Top dead center (TDC) on the compression stroke
  2. The angular position of the camshaft
    The code is triggered when the received signal does not match the expected values, often due to:
  • An erratic or absent signal
  • A mechanical misalignment
  • Electromagnetic interference

Common Symptoms

  • 🟠 Illumination of the check engine light (MIL)
  • Extended or failed starts
  • Unstable idle (if engine is running)
  • Loss of power (“limp mode”)
  • ⛽ Increased fuel consumption
  • Possible engine stalling

Possible Causes

(Ranked by frequency)

Cause Failure Mechanism
1. Electrical Issues Wiring near spark plug wires (interference)
Oxidized/damaged connectors (CPS or PCM)
Chafed/damaged wires
2. Component Failures Faulty camshaft sensor
Damaged reluctor wheel
3. Other Origins Incorrect engine timing
Spark plug/coil failure (false positive)

Diagnostic Procedure

Step 1: Preliminary Checks

  • Check the wiring condition:
    • Distance from high-voltage components (spark plugs, coils)
    • Absence of burns, exposed wires, or corrosion
  • Inspect the connectors (CPS and PCM): bent/broken pins

Step 2: Mechanical Inspection

  • Examine the reluctor wheel via the sensor housing (missing/deformed teeth)
  • Check the sensor shaft play (misalignment fault)

Step 3: Advanced Tests

  • Measure the CPS voltage (oscilloscope recommended):
    • Expected square wave signal (amplitude 0-5V or 0-12V depending on model)
  • Check the sensor resistance (manufacturer specifications)
  • Analyze related codes (P0340, P0342, etc.)

⚠️ Special Case: On some engines without a physical CPS, this code often indicates ignition failures (spark plugs, coils, or HT wires).

Recommended Solutions

Confirmed Failure Intervention
Faulty wiring Reroute/repair harnesses
Damaged connector Replace the connector or plug
CPS sensor faulty Replace the sensor (check gasket seal)
Damaged reluctor wheel Replace the camshaft (costly)
Ignition problem Test spark plugs/coils/HT wires

Key Technical Data

  • Timing tolerance: Deviation > 2-5° cam triggers the code
  • Quick test: Disconnect the CPS at idle → Engine should stall (otherwise PCM fault)
  • Statistics: 70% of P0341 codes are related to wiring or connectors (workshop data)

Critical recommendation: Always reset the PCM adaptations after repair. Use a diagnostic tool to clear the code and verify proper operation over 2 drive cycles.

Related Codes:
P0340 (Intermittent signal) – P0342 (Low signal) – P0343 (High signal)
P0345-P0349 (Bank 2 faults) – P0365-P0369 (Circuit “B” faults)