Code 12, No Distributor Reference Pulse To ECM

The ECM receives a pulse from the tach filter. When engine is not running and with no other codes stored, indicates a normal condition. Code 12 will not store in memory and will display only when fault is occurring. An open or ground between ignition coil and ECM will display Code 12.

1. Code 12 will display when ignition is on and ALDL connector is grounded. System is functioning normally. If "CHECK ENGINE" light does not flash, a fault should be suspected.
2. This checks if signal voltage is present at ECM.
3. This checks if a short or grounded condition exists between ignition coil and tach filter.