OBD-II P0335 Crankshaft Position Sensor A Circuit Malfunction

Understanding the OBD-II P0335 Code: Crankshaft Position Sensor A Circuit Malfunction

The OBD-II diagnostic trouble code P0335 signals a “Crankshaft Position Sensor A Circuit Malfunction”. This is a generic powertrain code applicable to vehicles equipped with OBD-II systems. While the code definition is universal, the specific diagnostic and repair procedures can differ based on the vehicle’s make and model.

At its core, the crankshaft position sensor (CKP) plays a crucial role in engine management. It monitors the position and rotational speed of the crankshaft, relaying this vital data to the Powertrain Control Module (PCM). The PCM utilizes this information for various functions, most importantly, to accurately time ignition spark and fuel injection. In some vehicle systems, the CKP sensor is primarily used for misfire detection and may not directly control spark timing.

The CKP sensor operates in conjunction with a reluctor ring, also known as a toothed ring, mounted on the crankshaft. As the reluctor ring rotates and its teeth pass the CKP sensor, it disrupts the sensor’s magnetic field. This interruption generates a square wave voltage signal. The PCM interprets these pulses as the crankshaft’s position and speed. When the PCM fails to receive consistent or plausible signals from the CKP sensor circuit, or detects an anomaly in the circuit itself, it triggers the P0335 code.

It’s important to note that there are related crankshaft position sensor codes, which may indicate similar or related issues within the system.

Common Symptoms Associated with a P0335 Code

The symptoms of a P0335 code can vary depending on the vehicle’s specific engine management system. If the CKP sensor is solely for misfire detection, the vehicle might still start and run, albeit with the Malfunction Indicator Lamp (MIL), or check engine light, illuminated. In some cases, the MIL might not illuminate immediately and could require multiple drive cycles to appear. Conversely, if the CKP sensor is critical for both misfire detection and spark timing, a P0335 code can lead to more significant drivability issues.

Here are some common symptoms associated with a P0335 code:

Engine No-Start Condition: In many cases, especially when the CKP sensor is vital for spark timing, the most prominent symptom is a vehicle that fails to start. The engine may crank, but it won’t fire up due to the lack of crankshaft position information.
Rough Running or Engine Misfires: If the vehicle does start, it may run erratically. This can manifest as a rough idle, hesitation, stumbling, or noticeable engine misfires. These issues arise from the PCM’s inability to accurately time ignition and fuel delivery.
Illuminated MIL (Malfunction Indicator Lamp): The check engine light will typically illuminate on the dashboard, indicating that the PCM has detected a fault within the engine management system.

Alt text: A close-up view of a crankshaft position sensor, highlighting its connector and sensor tip, crucial for diagnosing P0335 code.

Potential Causes of a P0335 Code

A P0335 code can be triggered by a range of issues affecting the crankshaft position sensor, its circuit, or related components. Accurately diagnosing the root cause is essential for effective repair.

Here are common culprits behind a P0335 code:

Damaged CKP Sensor Connector: The electrical connector to the CKP sensor is exposed to engine bay conditions and vibrations. It can become damaged, corroded, or loose, leading to intermittent or complete signal loss.
Damaged Reluctor Ring: The reluctor ring on the crankshaft must be intact and rotate correctly. Missing teeth, damage from debris, or a sheared-off keyway preventing its rotation will disrupt the CKP sensor signal.
Open Circuit in Sensor Output: An open circuit in the wiring between the CKP sensor and the PCM will prevent the signal from reaching the computer. This could be a broken wire, a severed connection, or corrosion within the wiring harness.
Short Circuit to Ground in Sensor Output: If the sensor output wire shorts to ground, the signal will be lost or distorted, as the voltage will be diverted to ground instead of reaching the PCM.
Short Circuit to Voltage in Sensor Output: A short circuit to a voltage source can also disrupt the CKP sensor signal, potentially sending an incorrect or constant voltage reading to the PCM.
Failed Crankshaft Position Sensor: The sensor itself can fail due to age, thermal stress, or physical damage. Internal sensor failure prevents it from correctly generating and transmitting the crankshaft position signal.
Broken Timing Belt or Timing Chain: In engines with timing belts or chains, if these components break or jump teeth, the relationship between the crankshaft and camshaft will be disrupted. This can cause a P0335 code, although other codes related to camshaft position may also be present.
Failed PCM (Powertrain Control Module): While less common, a faulty PCM can misinterpret signals or incorrectly diagnose sensor circuit issues. This is usually considered after ruling out other potential causes.

Diagnosing and Resolving a P0335 Code

Diagnosing a P0335 code requires a systematic approach, often starting with basic checks and progressing to more in-depth tests if necessary.

Here’s a step-by-step guide to diagnosing and resolving a P0335 code:

Initial Scan Tool Check: Use an OBD-II scan tool to confirm the presence of the P0335 code and check for any other related trouble codes. Crucially, monitor the scan tool’s live data stream for an RPM signal while cranking the engine.
RPM Signal Verification: If there is no RPM signal displayed on the scan tool during engine cranking, this strongly suggests an issue with the CKP sensor or its circuit.
Visual Inspection: Carefully inspect the CKP sensor and its connector. Look for any obvious damage, such as broken connectors, frayed wires, corrosion, or loose connections. Repair any visible damage as needed.

Alt text: Detailed inspection of a crankshaft position sensor connector, checking for corrosion, loose pins, and wire damage as part of P0335 diagnosis.

Sensor Signal Testing with a Scope (Optional but Recommended): If you have access to an oscilloscope, this is the most effective way to directly check the CKP sensor’s output signal. A healthy CKP sensor should produce a clear square wave pattern when the engine is cranked. An absent or distorted signal indicates a sensor or reluctor ring issue.
Resistance Testing (Using a Multimeter): If a scope is unavailable, consult a repair manual for your specific vehicle to obtain the correct resistance specification for the CKP sensor. Disconnect the sensor and use a multimeter to measure the sensor’s resistance. Compare the reading to the specified value.
PCM Connector Resistance Check (Advanced): For a more comprehensive check, and to rule out wiring issues, perform a resistance test directly at the PCM connector. This requires identifying the correct CKP sensor pins at the PCM. Compare this reading to the sensor specification. Caution: This step requires familiarity with automotive electrical systems and should be performed with care to avoid damaging the PCM.
Sensor Replacement (If Resistance is Out of Specification): If the sensor’s resistance is outside the specified range, replace the CKP sensor with a new, quality replacement part. After replacement, re-test for the RPM signal and clear the P0335 code.
Wiring and Circuit Troubleshooting (If Resistance is Okay at PCM): If the resistance readings are within specification at the PCM connector, the issue might be intermittent or related to wiring problems between the sensor and PCM. Carefully inspect the wiring harness for opens or shorts to ground or voltage. Repair any wiring faults and re-check for the RPM signal.
Wiggle Test: If the RPM signal is restored after wiring checks, perform a “wiggle test” on the wiring harness while monitoring the RPM signal. This involves gently wiggling and moving sections of the harness to try and induce the fault and identify intermittent connection issues.
PCM as a Last Resort: If all other tests fail to pinpoint the problem and the wiring and sensor appear to be functioning correctly, a faulty PCM is a possibility, although less likely. PCM diagnosis and replacement often require specialized tools and procedures.

Related OBD-II Trouble Codes

The P0335 code is closely related to other crankshaft position sensor codes and codes related to engine timing. Notably, P0385 Crankshaft Position Sensor “B” Circuit Malfunction is very similar, but refers to a secondary crankshaft position sensor in systems that utilize two sensors.

Other related codes include:

P0016, P0017, P0018, P0019: Crankshaft and Camshaft Position Correlation codes, indicating timing misalignment.
P0336, P0337, P0338, P0339: Codes related to CKP Sensor A range/performance and intermittent issues.
P0386, P0387, P0388, P0389: Codes related to CKP Sensor B range/performance and intermittent issues.

Need Further Assistance with P0335?

If you require more in-depth troubleshooting advice or want to share your experiences with a P0335 code, consider seeking assistance from online automotive repair forums. Engaging with experienced technicians and fellow car enthusiasts can provide valuable insights and support in resolving complex diagnostic issues.