Pcm Code E012, No Distributor (Tach) Signal: Action

PCM turns on SERVICE ENGINE SOON light.

Possible causes of no distributor reference pulses are open pick-up coil, HEI module unable to process pick-up coil signals or open or shorts on circuit No. 430 from module 5-wire connector to PCM.

1. This checks for proper output of HEI system. If voltmeter reads .5-2.8 volts, HEI module is receiving pick-up coil signal and producing reference pulses.
2. This checks for proper ground connections between PCM and engine and between PCM and HEI.
3. This checks for proper voltage through circuit No. 430 from HEI to PCM. If PCM terminal D8 sees .5-2.8 volts, PCM is receiving reference pulses.
4. If HEI will produce spark, fault is not within pick-up coil or module.