Hard Trouble Code E12: Notes

NOTE: If this code is not displayed during second pass of diagnostic codes, it is an intermittent failure and cannot be diagnosed using this procedure.

This code is set during cranking and results in a condition where the engine will not start. It indicates that distributor spark timing reference pulses, which are generated by pickup coil, are not being received by ECM. Possible causes are: No reference pulses generated by HEI system, defective wires, terminals, etc, or ECM not processing signal properly.

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).

Check for HEI reference pulses by disconnecting 4-way connector at distributor and measuring voltage between distributor connector pin B and ground. While cranking engine, voltage on pin B should be between 0.5 and 2.0 volts. If voltage is less than 0.5 volt or greater than 2.0 volts, HEI system should be checked with HEI tester. If no spark occurs during cranking, check HEI system. If spark does occur, then problem is in distributor harness or HEI module itself.
A voltage of 0.5-2.0 volts at pin B indicates that distributor spark timing reference pulses are present. Reconnect distributor connector. Reference pulses are carried through circuit No. 430 to ECM. Therefore, circuit No. 430 should be checked for an open or short to ground. With Blue ECM connector disconnected, measure voltage on circuit No. 430 while cranking. Signal of less than 0.5 volt indicates that wire is either open or shorted to ground. Signal of 0.5-2.0 volts indicates that wire is okay, check circuit No. 453 for an open. If circuit No. 453 is okay, check for faulty ECM connector or faulty ECM. Voltage greater than 2.0 volts on pin 2 indicates that circuit No. 430 is shorted to voltage.