Code P0334: Meaning, Causes, Symptoms, and Repairs

1. Meaning of Code P0334

Code P0334 is a generic powertrain diagnostic trouble code (DTC) applicable to vehicles equipped with OBD-II (Dodge, Ram, Ford, GMC, Chevrolet, VW, Toyota, etc.). Although generic, repair procedures may vary depending on the vehicle’s make and model.

This code indicates that the Powertrain Control Module (PCM) has detected an intermittent signal from the knock sensor for Bank 2.

• The Knock Sensor 2 may refer to a specific sensor (in a multi-sensor configuration) or a particular cylinder.
• Bank 2 refers to the side of the engine that does not contain cylinder number one.

Knock Sensor Operation

• The knock sensor is a piezoelectric sensor, typically threaded directly into the engine block.
• It produces a voltage when it detects vibrations from engine combustion.
• The PCM uses these signals to adjust ignition timing and prevent engine knock.

If the PCM detects an abnormal voltage (too high, too low, or intermittent), it logs a P0334 code and may illuminate the Check Engine Light.

Related fault codes include: P0324, P0325, P0326, P0327, P0328, P0329, P0330, P0331, P0332, and P0333.

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2. Severity and Symptoms of Code P0334

A P0334 code can indicate a serious problem, including internal engine failure. It should be diagnosed promptly.

Possible Symptoms:

• Reduced engine performance
• Hesitation during acceleration
• Unusual noises from the engine area
• Increased fuel consumption

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3. Possible Causes of Code P0334

Main causes of code P0334 include:

• Faulty knock sensor
• Internal engine malfunction
• Engine misfires
• Contaminated or poor-quality fuel
• Damaged knock sensor wiring and connectors
• PCM programming issue or failure

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4. Diagnostic and Repair Procedures

Required Tools:

• OBD-II scanner
• Voltmeter / Digital Ohmmeter (DVOM)
• Vehicle wiring diagrams and technical information

Diagnostic Steps:

1. Check Technical Service Bulletins (TSBs)
   • Consult TSBs to see if the issue is a known problem for the vehicle model.
2. Visual inspection of wiring and connectors
   • Look for damaged, burnt, or corroded wires.
   • Check the sensor connectors, often located on the lower part of the engine.
3. Reading codes with an OBD-II scanner
   • Retrieve stored fault codes and freeze frame data.
   • Clear the codes and perform a test drive to see if they return.
4. Testing the knock sensor
   • Use a voltmeter (DVOM) to check the voltage at the sensor connector.
   • Compare the values to the manufacturer’s specifications.
   • If the voltage is incorrect, suspect a faulty sensor or damaged wiring.
5. Checking the PCM
   • If the wiring and sensor are in good condition, the problem may lie with the PCM or a programming error.

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5. Safety Notes and Recommendations

• Beware of coolant! Some knock sensors are threaded into engine coolant passages. Allow the engine to cool before removing them to avoid burns.
• Multi-sensor systems vary by vehicle. Ensure you are addressing the correct knock sensor for the displayed code.
• A noisy engine can mask diagnosis. If the engine is making unusual noises, identify them before focusing on the knock sensor.

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Conclusion

Code P0334 can be caused by several factors, ranging from a faulty sensor to an internal engine failure. Accurate diagnosis by following the steps above will allow you to resolve the issue effectively and avoid potential engine damage.

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.

The crankshaft position sensor (CKP) measures the location of the crankshaft and transmits this information to the PCM (Powertrain Control Module).

Depending on the vehicle, the PCM uses this crankshaft position information to properly time the spark, or on some systems, it is only for misfire detection and does not control spark timing. The CKP sensor is fixed and works in harmony with a reluctor ring (or toothed ring) that is attached to the crankshaft. When this reluctor ring passes in front of the CKP sensor, the magnetic field created by the CKP sensor is interrupted, creating a square wave voltage signal that the PCM interprets as the crankshaft position. If the PCM detects that there are no crankshaft pulses or sees a problem with the pulses on the output circuit, P0335 will be set.

Crankshaft Position Sensor Trouble Codes:

• P0336 Crankshaft Position Sensor A Circuit Range/Performance
• P0337 Crankshaft Position Sensor A Circuit Low Input
• P0338 Crankshaft Position Sensor A Circuit High Input
• P0339 Crankshaft Position Sensor A Circuit Intermittent

Symptoms

NOTE: If the crankshaft position sensor is used only for misfire detection and NOT for spark timing (this varies by vehicle), the vehicle should start and run with an illuminated MIL (Malfunction Indicator Lamp). Additionally, some vehicles require multiple key cycles to illuminate the MIL. If this is the case, there may be no MIL illumination until the issue becomes frequent over time. If the crankshaft position sensor is used for both misfire detection and spark timing, the vehicle may or may not start.

Symptoms may include:

• Vehicle may not start
• Vehicle may run roughly or misfire
• MIL illumination

Causes

A P0335 check engine code could be caused by:

• Damaged CKP sensor connector
• Damaged reluctor ring (missing teeth or not rotating due to a sheared keyway)
• Open sensor output
• Sensor output shorted to ground
• Sensor output shorted to voltage
• Faulty crankshaft position sensor
• Broken timing belt
• Failed PCM

Possible Solutions

Using a scan tool, check if there is an RPM signal when the engine is cranking or running.
If there is no RPM reading, visually inspect the crankshaft sensor and connector for any damage and repair if necessary. If there is no visible damage and you have access to an oscilloscope, you can check the CKP’s 5-volt square wave pattern. If you don’t, obtain a resistance reading for your crankshaft sensor from a repair manual. (There are so many different types of crankshaft sensors that there is no way to indicate here what resistance value is correct). Then check the CKP sensor resistance by disconnecting the sensor and measuring the sensor’s resistance. (It is better to check resistance readings from the PCM connector. This rules out any wiring issues from the start. But this requires mechanical skills and should not be performed if you are not familiar with automotive electrical systems). Does the sensor meet resistance specifications?
If not, replace the CKP sensor. If it does, recheck the resistance reading from the PCM connector. Is the reading still correct?
If not, repair the open or shorted crankshaft sensor wiring and recheck. If the reading is correct, the problem is intermittent or the PCM may be at fault. Try reconnecting and checking the RPM signal again. If there is now an RPM signal, test the wiring harness to try to induce the fault.

This code is basically identical to P0385. This P0335 code refers to the “A” crankshaft position sensor, while P0385 refers to the “B” crankshaft position sensor. Other crankshaft sensor codes include P0016, P0017, P0018, P0019, P0335, P0336, P0337, P0338, P0339, P0385, P0386, P0387, P0388, and P0389.

What does this error code mean?

The diagnostic trouble code (DTC) in question is a generic powertrain code. It is considered generic because it applies to most vehicle makes and models (manufactured since 1996), although repair steps may vary slightly by manufacturer.

The crankshaft position sensor (CKP) is typically a two-wire device: one signal and one ground. This sensor usually consists of a permanent magnet mounted in front of a reluctor wheel (or toothed wheel), attached to the crankshaft. As this wheel passes in front of the sensor, an alternating (A/C) signal is generated. This signal varies with engine speed and is interpreted by the PCM (powertrain control module) to calculate engine RPM.

Some CKP sensors use Hall effect technology instead of a permanent magnet. These three-wire sensors operate using a power supply, ground, and signal. They also use a reluctor wheel, but their operation relies on a voltage change sent to the PCM, providing accurate engine speed data. This article focuses on permanent magnet sensors, which are more common and simpler in design.

CKP Sensor Operation

The crankshaft’s reluctor wheel has a specific number of teeth. Through this unique pattern, the PCM can not only identify the crankshaft’s position but also detect misfires by measuring variations in the CKP signal. Combined with the camshaft position sensor (CMP), the PCM can synchronize ignition and fuel injection. If the PCM detects a loss of signal, even momentarily, it may generate the error code P0336.

Error Codes Associated with the CKP Sensor:

• P0335: Crankshaft Position Sensor A Circuit Malfunction.
• P0337: Crankshaft Position Sensor A Circuit Low Input.
• P0338: Crankshaft Position Sensor A Circuit High Input.
• P0339: Crankshaft Position Sensor A Circuit Intermittent.

Symptoms of Code P0336:

• Intermittent stalling or failure to start.
• Difficulty starting the engine.
• Illumination of the Malfunction Indicator Lamp (MIL).
• Intermittent misfires.

Possible Causes:

1. Crankshaft sensor failure.
2. Damaged reluctor ring (broken teeth or debris).
3. Mispositioned or loose reluctor ring.
4. Damaged wiring harness causing a short circuit.
5. Open or faulty CKP wiring.

Possible Solutions:

Issues related to the CKP sensor can be intermittent, making diagnosis sometimes complex. Here are some steps to identify and resolve the problem:

1. Initial Check:
   If the engine stalls or fails to start, observe engine speed data using an oscilloscope or code reader. The absence of RPM reading indicates a potential issue with the CKP sensor.
2. Visual Inspection:
   Inspect the CKP sensor harness for cracks or damage. Ensure the cables are not near spark plug high-tension wires. Check connectors for loose or damaged connections.
3. Resistance Test:
   Remove the CKP sensor and measure its resistance according to the manufacturer’s specifications. If the resistance is out of range, replace the sensor.
4. Reluctor Ring Examination:
   Check the reluctor wheel for damage, broken teeth, or debris. Ensure the ring is properly secured to the crankshaft.
5. Repair or Replacement:
   If the ring is damaged or mispositioned, repair or replace it. Note that some reluctor rings are difficult to access, especially those located in the bell housing or behind the engine.

Note:

If, after checking the wiring and replacing the CKP sensor, the problem persists, it may be necessary to consult a professional to inspect hard-to-reach components.

What does it mean?

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

When I’ve diagnosed a stored P0337 code (in the past), it’s because the Powertrain Control Module (PCM) detected a low voltage input signal from the crankshaft position sensor (CKP) circuit.

CKP sensors are responsible for monitoring engine speed (RPM) and crankshaft position. These two factors are used in various engine management scenarios but are particularly important for ignition (spark) timing and fuel delivery.

The crankshaft position, especially relative to the camshafts, is one of the key factors used by the PCM to calculate ignition spark timing. Camshafts rotate at half the speed of the crankshaft, so it’s important that the PCM can distinguish between the engine’s intake and exhaust strokes (rotations). The CKP sensor and each camshaft position sensor (CMP) have at least one dedicated circuit to provide the PCM with an input signal, a 5-volt reference signal, and a ground.

CKP sensors are typically Hall effect electromagnetic types. They are mounted externally on the engine 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 one end of the crankshaft or integrated into the crankshaft itself.

The CKP sensor is mounted so that the crankshaft’s reluctor wheel passes very close to its magnetic tip. As the crankshaft rotates, the raised areas (on the reluctor wheel) complete an electromagnetic circuit with the sensor. When the gaps between the teeth pass the CKP sensor, the circuit is briefly interrupted. These circuit interruptions create voltage fluctuations that the PCM perceives as a waveform pattern.

With the engine running, the PCM continuously compares the input signals from the CKP and CMP sensors. If the CKP input signal voltage is lower than expected under certain circumstances, a P0337 code will be stored, and a MIL may be illuminated.

Other crankshaft position sensor fault codes include P0335, P0336, P0338, and P0339.

Code Severity and Symptoms

When a P0337 is stored, the engine will likely not run, and this code should be classified as severe. Even if the engine starts and runs, there is a high risk of no-start, and there will be driving repercussions.

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

Diagnostic and Repair Procedures

Before diagnosing a P0337 code, I need access to a suitable diagnostic scanner with an integrated digital volt/ohmmeter (DVOM) and an oscilloscope. I will also need access to All Data DIY (as a reliable source of vehicle information).

A viable starting point for any code diagnosis is a visual inspection of the wiring harnesses and connectors related to the system. Since petroleum-based fluids compromise the protective insulation of wiring and lead to short circuits or open circuits (and a stored P0337), circuits, electrical sensors, and/or connectors that have been contaminated by engine oil, coolant, or power steering fluid should be examined carefully.

If everything looks okay, connect the scanner to the vehicle’s diagnostic port and retrieve all stored fault codes and freeze frame data. I like to note this information down as it can be helpful if the P0337 proves to be intermittent.

Test the voltage on the CKP sensor in question. A five-volt reference is typically used for CKP sensor operation, but check the manufacturer’s specifications for the specific vehicle. There should also be a ground signal and one or more output circuits. If the reference voltage and ground circuits are detected at the CKP sensor connector, proceed to the next step.

After disconnecting the electrical connector from the CKP sensor in question, test it according to the manufacturer’s specifications using the DVOM. If the CKP sensor’s resistance levels do not meet the manufacturer’s specifications, replace it. If the CKP sensor matches the specifications, proceed to the next step. Reconnect the CKP sensor in question. Attach the oscilloscope’s positive test lead to the signal output wire and connect the negative lead to the sensor’s ground circuit. Now, power on the oscilloscope and select the appropriate voltage setting. With the engine running, observe the waveform on the oscilloscope, focusing on unexpected spikes or glitches. If spikes or glitches are observed, 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 missing voltage blocks are noticed in the waveform pattern, suspect a broken or worn reluctor ring or that the magnetic tip of the CKP sensor contains excessive metal debris. If no issues are detected in the waveform, proceed to the next step.

Connect the oscilloscope test leads to the CKP sensor signal input and ground circuits near the PCM connector and 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 the case, disconnect all associated controllers and begin testing individual circuits with the DVOM. Shorted or open circuits must be repaired or replaced. If the waveform pattern is identical to what was seen when the test leads were connected near the CKP sensor, suspect a faulty PCM or a PCM programming error.

Additional diagnostic notes:

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

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

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

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.

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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).

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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.

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Common Symptoms

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

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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.

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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.

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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.

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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.

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Estimated Costs

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

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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.

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.

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.

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.