Crankshaft Position Sensor "A" Circuit
The crankshaft sensor tells the engine computer how fast the engine is turning and where the pistons are; without that signal it cannot decide when to fire the spark or inject fuel.
What the car has detected
The engine computer is not receiving the crankshaft sensor signal (for example, the engine has been cranking for several seconds without a single pulse) or the signal is wrong. If the sensor is completely dead, the engine may not start and sometimes the code is not even stored.
The engine may cut out while driving or fail to restart, which is dangerous on the road. Have it checked as soon as possible and avoid long trips.
Symptoms
- Engine warning light on
- The engine won't start or takes a long time
- The engine cuts out while driving, sometimes when hot
- Hesitation or misfires
- Rev counter behaving oddly
Possible causes
- Failed crankshaft sensor
- Damaged wiring or a corroded connector
- Metal debris stuck to the sensor tip
- Damaged or shifted crankshaft reluctor wheel
- Engine computer fault (rare)
Checks for the garage
- Check the battery and charging voltage: low voltage disturbs signals
- Save all codes and the freeze frame data before clearing
- Check the connector and wiring, and the sensor tip for debris
- Check the sensor signal while cranking with an oscilloscope or diagnostics
- Measure the sensor's supply (usually 5 V) and earth
- Replace the sensor only after testing the circuit
Next step
Check the battery and have the crankshaft sensor, its connector, its wiring and the toothed wheel it reads checked.
Go to a garage as soon as possible; if the car won't start, it may need towing. Checking the signal needs an oscilloscope or diagnostics.