Volvo All Engines (2004 Emissions) Fault Code: SID 21 FMI 8 Cam Speed Sensor

Fault Condition: Management System (EMS) Module senses a significant difference between the engine speed calculated from the CAM Speed Sensor signal and the engine speed calculated from the Crank Speed Sensor, the EMS Module will turn on the Electronic Malfunction Light, and code SID 21 will set. If the signals return to normal, the code will become inactive. The engine must be running to set an active CAM Speed Sensor fault code.

Note: Electrical problems can cause this fault to be generated, and electrical diagnostics are provided in this section. Mechanical problems can also cause temporary or permanent speed signal errors. After all electrical possibilities have been ruled out, check mechanical conditions that could cause vibration or signal errors. Such conditions include but are not limited to:
Faulty Engine Vibration Damper, Contaminated sensor tips, Contaminated Cam Gear face, Excessive Camshaft end play, Improperly adjusted sensor, Improperly balanced engine components, Faulty engine timing cover.

Possible repairs:

Turn the ignition key OFF first.

1) Disconnect the CAM Speed Sensor. Measure the resistance between terminals 1 and 2 on the CAM Speed Sensor. If the resistance is not between 775–945 ohms check the CAM Speed Sensor pigtail connector and wiring for damage. If the connector and wiring are not damaged, replace the CAM Speed Sensor.
2) Disconnect the CAM Speed Sensor connector. Measure the resistance between sensor pin 1 and a good ground and between sensor pin 2 and a good ground. If continuity exists between either pin and ground, replace the sensor.
3) Disconnect connectors A and B from the EMS Module. Disconnect the CAM Speed Sensor connector. Check for continuity between EMS Module connector A pin 45 and all other pins on EMS Module connectors A and B.
If continuity exists, pin 45 is shorted to one of the other EMS Module circuits. Locate and repair the short circuit to voltage. If there is NO continuity, the sensor return line is shorted to voltage somewhere else in the harness. Locate and repair the short circuit to voltage.
4) Disconnect connectors A and B from the EMS Module. Disconnect the CAM Speed Sensor. Check for continuity between EMS Module connector A pin 46 and all other pins on EMS Module connectors A and B. If continuity exists between pin 46 and any other pin, pin 46 is shorted to one of the other EMS Module circuits. Locate and repair the short circuit to voltage. If there is NO continuity, the sensor return line is shorted to voltage somewhere else in the harness. Locate and repair the short circuit to voltage.
5) Disconnect the CAM Speed Sensor. Disconnect EMS Module connectors A and B. Check for continuity between EMS Module connector A pins 45 and 46 versus all other pins on EMS Module connectors A and B. If continuity exists, the suspect pin is shorted to one of the other EMS Module circuits. Locate and repair the short circuit.
6) Disconnect the CAM Speed Sensor. Disconnect EMS Module connectors A and B. Check for continuity between the circuit (connector A pin 45 or 46) that showed continuity in test 7, versus all other pins on EMS Module connectors A and B. If continuity exists, the suspect pin is shorted to one of the other EMS Module circuits. Locate and repair the short circuit. If there is NO continuity, the suspect circuit is shorted to ground somewhere else in the harness. Locate and repair the short circuit.
7) Connect the CAM Speed Sensor. Disconnect EMS Module connector A. Measure the resistance between EMS Module connector A pins 45 and 46. If the resistance is not within this range, the CAM Speed Sensor has an open circuit or a faulty connector. Repair the connector if possible, otherwise, replace the sensor.
8) Connect the CAM Speed Sensor connector. Connect EMS Module connectors A and B. Start the engine. If blink code SID 21 is still active, check the EMS Module and connectors for dirt, loose or broken pins, or repairable damage. If no problems are evident, or they are not repairable, replace the EMS Module and retest the system. If blink code SID 21 is NOT active, the diagnostic procedures have corrected the problem. Check all connectors to ensure proper connections.