2.2.185. SPN 4201, FMI 2, Crankshaft speed sensor: Signal erratic, too much noise pulses.

Description

The crankshaft speed sensor signal is not valid.

Possible causes are:

  • The sensor wiring is defective.
  • The sensor is defective.
  • The distance between the sensor and the trigger wheel is too high.
  • An external electromagnetic disturbance is affecting the sensor signal.
  • The trigger wheel is defective.

Reaction in EEM

The FC is stored and the warning lamp is activated. The CAN message indicates an active fault. Engine power is reduced (Degradation Level 2). The engine starting may take longer than normally, and the running may be poor due to missing/incorrect information for the injection timing control. The engine runs with the camshaft speed sensor signal.

Solution

First save the error log and then do the procedure that follows:

  • Examine the crankshaft sensor wiring, the connectors and the contact surfaces of the connector pins (possible oxidation). Look also for a possible reverse connection.
  • Measure the coil resistance of the crankshaft sensor (the engine must be stopped). The normal resistance values are + 20°C is 1120 - 1530 Ohms.
  • Examine the crankshaft sensor mounting. The air gap between the sensor tip and the trigger wheel teeth should be 0,5 - 1,2 mm.
  • Look for possible electromagnetic noise sources on or close to the vehicle, disturbing the speed sensor signal (devices using or carrying high currents, high voltages or strong magnetic fields).
  • Check the condition and the mounting of the crankshaft trigger wheel (damaged teeth, the positioning of the trigger wheel).
  • Test the operation with another crankshaft speed sensor to see if the sensor is defective.

See Crankshaft speed sensor for reference.