P0335

What Does Code P0335 Mean?

DTC P0335 signifies a detected “Crankshaft Position Sensor A Circuit Malfunction.” The Crankshaft Position (CKP) sensor is a critical input device for the Engine Control Module (ECM) or Powertrain Control Module (PCM), responsible for monitoring the rotational speed and precise angular position of the crankshaft. This data is fundamental for the ECM to calculate engine RPM, synchronize ignition timing, and determine fuel injection pulse width and timing. The “A” in the code typically refers to the primary CKP sensor on the engine. A “circuit malfunction” indicates that the ECM is detecting an implausible, intermittent, or absent signal from the CKP sensor circuit, or that the signal characteristics are outside of its expected operating parameters. This does not necessarily mean the sensor itself has failed, but rather that an issue exists anywhere within the circuit, including the sensor, its wiring, the electrical connector, or even the ECM itself. The ECM sets this code when it cannot reliably interpret the crankshaft position, which directly impacts its ability to control critical engine functions.

Common Symptoms

• No-start condition: The engine cranks but fails to ignite, as the ECM cannot determine crankshaft position for spark and fuel timing.
• Engine stalling: The engine may suddenly shut off while driving or at idle, often failing to restart immediately.
• Intermittent misfires or rough idle: Erratic or incorrect crankshaft position data can lead to improper spark and fuel delivery.
• Reduced engine performance: Loss of power, hesitation, or poor acceleration due to compromised engine timing.
• Illuminated Check Engine Light (CEL): The Malfunction Indicator Lamp (MIL) will be activated.
• Erratic tachometer readings: In some cases, an intermittent signal can cause the tachometer to jump or drop unexpectedly.

What Causes the Code P0335?

• Faulty Crankshaft Position Sensor (CKP): The sensor itself may have an internal short, open circuit, or degraded magnetic/Hall effect element, preventing accurate signal generation.
• Damaged Wiring Harness: Frayed, chafed, shorted, or open wires in the CKP sensor circuit. This can include insulation damage from heat, vibration, or rodent activity.
• Poor Electrical Connection: Corroded, loose, or damaged terminals/pins within the CKP sensor connector or the ECM connector.
• Damaged Reluctor Ring/Tone Wheel: A bent, damaged, or missing tooth on the crankshaft-mounted reluctor ring can prevent the sensor from generating a consistent and accurate signal.
• Engine Control Module (ECM/PCM) Malfunction: Although less common, an internal fault within the ECM’s input circuit for the CKP sensor can lead to this code.
• Incorrect Sensor Installation/Air Gap: If the sensor was recently replaced, an improper air gap between the sensor and the reluctor wheel can cause an inconsistent signal.

How to Diagnose and Troubleshoot

Diagnosing P0335 requires a systematic approach, often utilizing an OBD-II scanner, digital multimeter (DMM), and potentially an oscilloscope.

1. Visual Inspection:
   • Begin with a thorough visual inspection of the CKP sensor and its associated wiring harness. Look for any signs of physical damage, such as frayed or exposed wires, melted insulation, or corrosion. Pay close attention to areas where the wiring might rub against engine components.
   • Inspect the CKP sensor electrical connector for bent or corroded pins, proper seating, and any signs of moisture intrusion.
   • If accessible, visually inspect the crankshaft reluctor ring (also known as the tone wheel or trigger wheel) for missing teeth, damage, or excessive debris accumulation that might interfere with the sensor’s reading.
2. OBD-II Scanner Data Analysis:
   • Connect an OBD-II scanner and check for pending or stored codes. Note any other related codes, especially those pertaining to camshaft position sensors (e.g., P0340, P0341), as they might indicate a broader engine timing issue.
   • Access live data parameters, specifically monitoring “Engine RPM” and “Crankshaft Position Sensor” readings. During engine cranking (if it doesn’t start), observe the RPM value. If the RPM remains at zero or is erratic, it strongly suggests a problem with the CKP sensor or its circuit. Compare the CKP sensor signal to the Camshaft Position (CMP) sensor signal if available; they should typically show a consistent correlation.
3. Digital Multimeter (DMM) Testing:
   • Power and Ground Check (Sensor Disconnected): Disconnect the CKP sensor connector. With the ignition ON, use a DMM to measure the voltage at the sensor’s power supply wire (typically 5V or 12V, consult vehicle-specific wiring diagrams). Also, verify a good ground connection on the ground wire. Absence of power or ground indicates a wiring issue from the ECM.
   • Sensor Resistance Check (for Inductive Sensors): For 2-wire magnetic inductive CKP sensors, measure the resistance across the sensor’s terminals using the DMM. Compare the reading to the manufacturer’s specifications (typically 200-2500 ohms). An open circuit (OL) or a reading significantly outside the specified range indicates a faulty sensor. Hall effect sensors (typically 3-wire) do not have a measurable resistance value.
   • Signal Wire Continuity and Short Checks (Sensor and ECM Disconnected): Disconnect both the CKP sensor and the ECM connectors. Use the DMM to check for continuity on each wire from the sensor connector to the ECM connector. Any high resistance or open circuit indicates a wiring break. Also, check each wire for a short to ground and a short to voltage.
4. Oscilloscope Analysis (Recommended for Signal Integrity):
   • For precise diagnosis, an oscilloscope can be used to capture the actual waveform generated by the CKP sensor while cranking or running the engine. This allows for verification of the signal’s amplitude, frequency, and pattern, identifying any inconsistencies, dropouts, or noise that a DMM might miss. Compare the waveform to a known good pattern from the service manual.

Recommended Repairs and Solutions

Based on the diagnostic findings, the following repairs are typically recommended:

• Replace the Crankshaft Position Sensor: If the DMM tests or oscilloscope analysis confirm the sensor itself is faulty (e.g., incorrect resistance, no signal output, or a distorted waveform), replace it with an OEM-equivalent or high-quality aftermarket part. Ensure proper seating and torque to maintain the correct air gap.
• Repair or Replace Wiring Harness: If visual inspection or continuity tests identify damaged wires, perform professional repairs using appropriate crimps, solder, and heat-shrink tubing. For extensive damage, replacement of the affected section of the wiring harness may be necessary.
• Clean or Repair Electrical Connector: If corrosion, loose terminals, or bent pins are found in the connector, clean them thoroughly with electrical contact cleaner, or replace the connector housing and terminals as needed to ensure a secure and reliable connection.
• Inspect and Replace Reluctor Ring: If the reluctor ring on the crankshaft is found to be damaged, bent, or missing teeth, it must be replaced. This is often a more involved repair, potentially requiring removal of the crankshaft pulley or even partial engine disassembly, depending on its location.
• ECM Replacement/Reprogramming: Only consider ECM replacement as a last resort after thoroughly exhausting all other diagnostic possibilities and confirming an internal ECM fault through specific vehicle diagnostic procedures. ECMs are expensive and typically require programming or coding to the vehicle.

Mechanic’s Tip: After any repair involving the CKP sensor or its circuit, it is crucial to clear the Diagnostic Trouble Codes (DTCs) from the ECM using an OBD-II scanner. Perform a thorough test drive, covering various engine speeds and loads, to ensure the fault does not return and that the ECM’s readiness monitors are set. Some vehicles may require a crankshaft position sensor relearn procedure after replacement to recalibrate the ECM to the new sensor’s signal. Always consult the specific vehicle service manual for this procedure.