Volvo All Engines (2010 Emissions) Fault Code: SPN 636 FMI 8 PID: SID 21 Camshaft Position Sensor (CMP)

The camshaft position (CMP) sensor is an inductive device. As the camshaft turns, the tip of the CMP sensor senses the teeth of the tone wheel fastened to the camshaft vibration damper. The CMP sensor sends a series of voltage pulses to the Engine Control Module (ECM). The frequency of the pulses is translated into engine speed (RPM) and position by the ECM. The ECM uses this information along with the information from Crankshaft Position (CKP) sensor to synchronize fuel injection.

Conditions for diagnostic trouble code (DTC):
1) Engine Control module (ECM) detects extra pulses on the crankshaft position (CKP) signal

Observable symptoms
1) Difficult to start at next start despite that no diagnostic trouble code (DTC) is set when the engine is running
2) Loss of power

Probable cause
1) Camshaft Position (CMP) Sensor
2) Wiring harness
3) Tooth wheel

Detailed information
1) Electrical interference in the crankshaft position (CKP) sensor signal
2) Incorrectly installed sensor (incorrect distance to tooth wheel)
3) Poor insulation