Code P012, No 4X Reference Signal From IGN Control Module: Action

PCM turns on Malfunction Indicator Light (MIL).

1. Checks to see if Code P035 is present because a REF LO problem can cause other ignition problems.
2. If Code P012 is current, the condition still exists and can be diagnosed directly. If Code P012 is history, look at snapshot data to determine conditions under which code was set.
3. Check for proper output of electronic ignition system. If voltmeter reads 4.1 volts or greater, ignition control module is able to produce 4X reference pulses.
4. Checks to see if Code P012 was set while vehicle was running or not, if MAP value is 80 kPa or less, or if engine was running when code was set. Stray cam pulses with ignition on, engine not running can also cause a false Code P012 to set.
5. Checks for 4X reference pulses on circuit No. 430 from ignition control module to PCM. If PCM terminal No. 3E2 has been between 30-100 Hertz, PCM is receiving 4X receiving pulses.
6. Checks if a faulty PCM is pulling the 4X signal low.
7. Checks for short to voltage on circuit No. 430.
8. Checks if ICM is providing proper reference signal to PCM.

Fig 1: Code P012 Schematic, No 4X Reference Signal From IGN Control Module

Courtesy of GENERAL MOTORS CORP