OBD2 P0335 Code: Crankshaft Position Sensor A Circuit Malfunction Explained

The trouble code P0335 is a common OBD-II (On-Board Diagnostics II) code indicating a Crankshaft Position Sensor A Circuit Malfunction. This code signals a problem within the crankshaft position sensor circuit, which is crucial for your vehicle’s engine management system. As an expert from carparteu.com, I’ll break down what this code means, its symptoms, potential causes, and how to troubleshoot and fix it.

Understanding the Crankshaft Position Sensor (CKP)

The Crankshaft Position Sensor (CKP) is a vital component in your car’s engine. It monitors the position and rotational speed of the crankshaft. This information is relayed to the Powertrain Control Module (PCM), also known as the engine control unit (ECU). The PCM uses this data for several critical functions, including:

• Ignition Timing: In many vehicles, the PCM relies on the CKP sensor to precisely time the spark plugs, ensuring optimal combustion.
• Fuel Injection Timing: Accurate crankshaft position data is also essential for proper fuel injection timing, maximizing engine efficiency.
• Misfire Detection: Even in systems where the CKP doesn’t directly control spark timing, it’s often used for detecting engine misfires.

The CKP sensor typically works with a reluctor ring (or toothed ring) attached to the crankshaft. As the reluctor ring rotates, it passes by the CKP sensor. This interaction disrupts the magnetic field of the sensor, generating a square wave voltage signal. The PCM interprets these pulses as crankshaft position and speed.

When the PCM detects missing pulses, irregularities in the signal, or a complete lack of signal from the CKP sensor circuit, it will register the P0335 code.

Symptoms of a P0335 Code

The symptoms of a P0335 code can vary depending on whether the CKP sensor is solely used for misfire detection or also controls spark timing.

In cases where the CKP sensor is only for misfire detection:

• Check Engine Light (MIL) Illumination: The most consistent symptom is the illumination of the Malfunction Indicator Lamp (MIL), or check engine light, on your dashboard.
• Vehicle May Start and Run (Potentially with Issues): The vehicle might still start and run, as the engine management system may rely on other sensors for primary timing. However, performance issues are still possible.
• Delayed MIL Illumination: Some vehicles require multiple drive cycles with the fault present before the MIL illuminates.

In cases where the CKP sensor is crucial for spark timing:

• Vehicle May Not Start: If the PCM cannot get a reliable signal from the CKP sensor for timing, the engine may fail to start altogether.
• Rough Running or Misfiring Engine: If the engine does start, it may run very rough, experience significant misfires, and lack power.
• Check Engine Light (MIL) Illumination: The MIL will likely illuminate.

Potential Causes of a P0335 Code

Several factors can trigger a P0335 code. Here’s a breakdown of the common culprits:

• Faulty Crankshaft Position Sensor: The sensor itself may be defective due to age, wear, or damage.
• Damaged CKP Sensor Wiring or Connector: Wiring to the sensor can become frayed, broken, or corroded. The connector can also be damaged, leading to poor electrical connection.
• Reluctor Ring Damage: The reluctor ring on the crankshaft can be damaged (missing teeth, bent, or misaligned), preventing proper signal generation. In extreme cases, a sheared-off keyway can stop the reluctor ring from turning altogether.
• Open Circuit in Sensor Output: A break in the wiring leading from the sensor can cause an open circuit.
• Short Circuit to Ground or Voltage: The sensor output wire might be shorted to ground or to a voltage source, disrupting the signal.
• Timing Belt/Chain Issues: In rare cases, a broken or severely stretched timing belt or chain can affect the crankshaft position sensor signal, although this usually causes more severe engine problems and other DTCs.
• Failed PCM (Powertrain Control Module): While less common, a faulty PCM can misinterpret sensor signals or incorrectly set the P0335 code.

Diagnosing and Repairing a P0335 Code

Troubleshooting a P0335 code requires a systematic approach. Here’s a step-by-step guide for diagnosis and potential solutions:

1. Check for RPM Signal with a Scan Tool: Use an OBD-II scan tool to check for an RPM signal while cranking the engine.

   • No RPM Signal: This strongly suggests a problem with the CKP sensor, its circuit, or the reluctor ring. Proceed to step 2.
   • RPM Signal Present: The issue might be intermittent, or the problem could lie elsewhere. Wiggle test the wiring harness while monitoring the RPM signal to see if you can induce a fault. If the RPM signal is erratic or drops out during the wiggle test, suspect a wiring issue.

2. Visual Inspection of CKP Sensor and Connector: Carefully inspect the CKP sensor and its connector for any visible damage. Look for:

   • Physical Damage: Cracks, breaks, or impact damage to the sensor.
   • Connector Issues: Loose connections, corrosion, bent or broken pins, or damage to the connector housing.
   • Wiring Problems: Frayed, cut, or melted wires near the sensor and along the wiring harness.

   Repair any visible damage to wiring or connectors. Clean corroded connectors and ensure a secure connection.

3. Check CKP Sensor Resistance: Consult your vehicle’s repair manual for the specified resistance range for your CKP sensor.

   • Disconnect the CKP sensor and use a multimeter to measure the sensor’s resistance.

   • Compare the reading to the specification.

   • Out of Specification: Replace the CKP sensor.

   • Within Specification: The sensor itself might be okay, but there could still be wiring issues. Proceed to step 4.

4. Check Resistance from PCM Connector (Advanced): This step requires more advanced skills and caution. If you are not comfortable working with automotive electrical systems, it’s best to consult a qualified mechanic.

   • Locate the PCM connector and identify the CKP sensor signal wires (refer to a wiring diagram for your vehicle).

   • Measure resistance from the PCM connector pins (where the CKP sensor wires connect) back to the CKP sensor connector (still disconnected).

   • Compare the reading to the sensor specification. This test includes the wiring in the circuit.

   • Reading is now out of spec (different from sensor test): Indicates a wiring problem (open or short) between the PCM and the CKP sensor. Repair the wiring as needed and re-test.

   • Reading is still within spec: The wiring is likely good. The problem may be intermittent, or the PCM could be at fault (less likely).

5. Replace CKP Sensor (If Necessary): If the sensor resistance is out of specification, or if visual inspection and wiring checks haven’t revealed the problem, replacing the CKP sensor is often the next step. Ensure you use a quality replacement sensor that is compatible with your vehicle.

6. Re-test and Verify Repair: After any repairs, clear the P0335 code using your scan tool. Start the engine and check if the code returns. Monitor for RPM signal stability and engine performance.

Important Notes:

• Related Codes: Be aware that P0335 is closely related to P0385 (Crankshaft Position Sensor “B” Circuit Malfunction) if your vehicle has two CKP sensors. Other related codes involve camshaft position sensors (P0016-P0019) and other CKP sensor circuit issues (P0336-P0339, P0386-P0389).
• Professional Help: If you are not comfortable with electrical testing or car repair, it’s always best to seek assistance from a qualified automotive technician to diagnose and repair a P0335 code.

By following these steps, you can effectively diagnose and address a P0335 code and get your vehicle running smoothly again. Remember to prioritize safety and consult a professional if you are unsure about any step in the process.