3.2.488. SPN 723, FMI 31, Cam speed sensor signal missing

Description

The system has not been able to detect any signals from the camshaft sensor.

Possible causes are:

  • An invalid signal or no signal from the camshaft sensor.
  • The sensor wiring is defective (signal lines reversed).
  • The sensor is defective.
  • The trigger wheel is defective.

Reaction in EEM

The FC is stored and the warning lamp is activated. The CAN message indicates active fault. Engine power will be 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 crankshaft speed sensor signal.

Solution

First save the error log and then erase it. Restart the ECU after erasing the error log. If the fault occurs again during the next driving cycle, check the following paths:

  • Check the camshaft sensor wiring, the connectors and the contact surfaces of the connector pins (possible oxidation). Look for possible reverse connection.
  • Check the coil resistance of the camshaft sensor (the engine must be stopped). The normal resistance values are + 20°C is 774 - 946 Ohms.
  • Check the camshaft sensor mounting. The air gap between the sensor tip and the trigger wheel teeth should be 0,2 - 1,0 mm.
  • Check the condition of the camshaft trigger wheel. A damaged tooth may generate an abnormal pulse shape.
  • Check the operation with another camshaft speed sensor to see if the sensor is defective.

See Camshaft speed sensor for reference.