Why Do They Fail?

Crankshaft position sensors operate in demanding environments and can fail for a number of reasons, including:

• Internal sensor degradation caused by age, wear and deterioration of the magnetic or Hall effect sensing element.
• Prolonged exposure to heat and vibration from their location close to the engine block, flywheel or crankshaft.
• Damage to the reluctor wheel such as missing teeth, distortion or excessive wear, resulting in inaccurate signal generation.
• Oil, coolant or debris contamination affecting sensor performance and signal quality.
• Wiring and connector faults caused by corrosion, vibration damage or poor electrical connections.
• Incorrect sensor air gap resulting from installation issues or component wear.

Crankshaft position sensor faults may be intermittent or permanent, often making accurate diagnosis dependent on live data analysis or oscilloscope testing.

Symptoms of a Failed Crank Angle Sensor

When a crankshaft position sensor begins to fail or provides an intermittent signal, common symptoms may include:

• Intermittent or complete no-start conditions, particularly when the engine is hot.
• Engine stalling during driving or at idle due to loss of crankshaft position information.
• Illuminated Engine Management Light (MIL) accompanied by crankshaft position or engine synchronisation fault codes.
• Rough idle, hesitation or misfiring caused by inaccurate ignition and injection timing.
• Reduced engine performance and increased fuel consumption.
• Limp-home mode activation or a crank-but-no-start condition where spark and fuel delivery are inhibited.

Because crankshaft position sensor faults can mimic a variety of ignition, fuel and timing-related issues, accurate diagnosis should always include live data analysis or oscilloscope testing to verify signal integrity.

Fitting Tips

• Inspect the sensor connector and wiring harness for signs of corrosion, damage, chafing or oil contamination before replacement.
• Avoid over-tightening and always follow the vehicle manufacturer's torque specifications, particularly where sensors are mounted in plastic housings.
• Clean the mounting surface and verify the sensor air gap where applicable, ensuring accurate signal generation from the reluctor wheel.
• Inspect the reluctor wheel for missing teeth, distortion or damage that could mimic sensor failure.
• Check live engine speed data using a diagnostic scan tool or oscilloscope rather than relying solely on stored fault codes.
• Clear fault codes and complete any required relearn procedures after installation to ensure correct ECU operation.

Not sure whether the fault lies with the sensor, wiring or reluctor wheel? Our TechASSIST team can help guide you through live signal diagnostics and best-practice installation procedures.