2.2.400. SPN 723, FMI 8, Cam speed sensor: Signal offset between crankshaft and camshaft too large

Description

The timing between the crankshaft and the camshaft signals deviates too much.

Possible causes are:

  • An invalid signal from the crankshaft sensor or from the camshaft sensor.
  • Mechanical timing between camshaft and crankshaft is not correct.
  • The distance between the sensor and the trigger wheel is too high, possibly a loose sensor.

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 and the camshaft sensor wiring, the connectors and the contact surfaces of the connector pins (possible oxidation).
  • Measure the coil resistance of the sensors (the engine must be stopped). The normal resistance values are + 20°C is 1120 - 1530 Ohms.
  • Examine the speed sensor mounting. The air gap between the sensor tip and the trigger wheel teeth should be 0,5 - 1,2 mm.
  • Verify that the timing between the camshaft and crankshaft is correct.
  • 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).
  • Examine the condition and the mounting of the trigger wheel (damaged teeth, the positioning of the trigger wheel).
  • Test the operation with another crankshaft or camshaft speed sensor to see if the sensor is defective.

See Camshaft speed sensor for reference.

See Crankshaft speed sensor for reference.