DTC 12, No Rpm Signal: Notes

PCM monitors Crankshaft Position (CKP) sensor and Camshaft Position (CMP) sensor. PCM receives an AC voltage signal from CMP and CKP sensors. This voltage is produced when engine is running. A fluctuating magnetic field is generated due to changes in air gap between CMP sensor and distributor shaft signal rotor and between CKP sensor and interrupter ring. This voltage is toggled high and low which enables PCM to determine crank angle and camshaft position. PCM uses this information to determine when to fire ignition coil and fuel injectors. DTC 12 will set if PCM does not detect crank angle input while engine is cranking for 2 seconds or more, or PCM does not detect camshaft position input with engine speed 600-4000 RPM for 3 seconds or more.

1. Checks resistance of CKP sensor.
2. Checks resistance of CMP sensor.
3. Checks for an open in Black wire between PCM and CKP sensor.
4. Checks for an open in White wire between PCM and CKP sensor.
5. Checks for an open in White wire between PCM and distributor.
6. Checks for an open in Black wire between PCM and distributor.
7. Checks for a short to voltage or a short to ground in Black wire between PCM and CKP sensor.
8. Checks for a short to voltage or a short to ground in Black wire between PCM and distributor.
9. Check for a short to voltage or a short to ground in White wire between PCM and CKP sensor and between PCM and distributor.
10. Check signal rotor air gap and faulty PCM.