A failing crankshaft position sensor typically triggers DTCs in the P0335–P0338 family, and often P0339 if the signal is intermittent. You may also see misfire or no-start codes like P0300 or P0301–P0308 when timing information is unreliable.
The crankshaft position sensor (CKP) is a critical timing reference used by the engine control unit (ECU) to determine the position and speed of the crankshaft. When the sensor or its circuitry deteriorates, the ECU can’t reliably read engine speed, which can lead to stalling, hard starts, reduced power, and misfires. This article explains which codes are typically associated with a bad CKP sensor and how to approach diagnosis and fixes.
Common diagnostic trouble codes associated with a bad crankshaft sensor
The most frequently seen codes linked to CKP faults describe circuit integrity and signal quality. Here are the standard DTCs you’ll want to know.
- P0335 Crankshaft Position Sensor A Circuit Malfunction
- 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
Engine fault codes in this family point to the CKP's electrical circuit or the quality of its signal. A bad CKP sensor can also cause the engine to fail to start or to stall unexpectedly, depending on the severity of the fault.
Related symptoms and misfire codes that may accompany CKP failure
Because the CKP informs the ECU about crank position, failures often ripple into drivability issues and misfire codes. The following codes commonly appear when timing information is unreliable, though they can have other causes as well.
- P0300 Random/Multiple Cylinder Misfire Detected
- P0301–P0308 Cylinder-specific Misfire Codes (depending on engine configuration)
If you observe misfire codes in conjunction with CKP-related codes, it’s important to consider the possibility of an intermittent signal or timing disturbance. A thorough inspection should cover the CKP sensor, its wiring, the reluctor ring, and the ECU/PCM connections.
Diagnostics and fixes
Initial checks
Begin with a visual inspection of the CKP wiring and connector and inspect the reluctor ring for damage or debris. Ensure the sensor is properly mounted and that there are no broken wires or bent pins in the harness.
- Inspect the CKP connector for corrosion, bent pins, and proper seating.
- Check the wiring harness for cuts, frayed insulation, or heat damage.
- Inspect the reluctor ring for missing teeth or damage that would affect the sensor's readings.
- Verify the sensor is secured to spec and not moved out of position.
Addressing simple mechanical or wiring issues can resolve some CKP faults without replacement. If the problem persists, proceed to electrical testing.
Electrical testing
Use a scan tool to monitor CKP live data and, if available, an oscilloscope or a specialty CKP tester to verify signal quality. Compare against the vehicle's service manual specifications.
- Check CKP signal in real time to confirm a clean, stable waveform; look for intermittent dropouts or jitter.
- Test sensor resistance and verify it falls within the manufacturer’s specified range; replace if out of spec.
- Check voltage supply and ground to the CKP sensor and ensure the reference voltage is stable.
If the signal is erratic or absent, replacement of the CKP sensor is often indicated, followed by clearing codes and rechecking system timing.
Replacement and follow-up
Replacing a verified faulty CKP sensor is typically straightforward, but it should be done with the engine off and with proper torque on the sensor mounting to avoid misalignment. After replacement, clear the codes and test drive the vehicle to verify the issue is resolved. If problems persist, further diagnosis may be necessary to rule out ECU or wiring fault elsewhere.
Summary
A bad crankshaft position sensor most commonly triggers DTCs in the P0335–P0338 family, with P0339 indicating an intermittent condition. Misfire and no-start codes, such as P0300 and P0301–P0308, can accompany CKP faults. Diagnosis should start with a visual inspection of wiring and connectors, followed by electrical testing of the sensor and circuit, and finally replacement if the fault is confirmed. Proper diagnostics can restore reliable starting and smooth operation.