P012

Circuit Description

The PCM checks for CAM pulses being received without 4X reference pulses. If the PCM senses no reference pulses, the engine will not start because the fuel delivery system is triggered by the reference pulses and Code P012 is set.

NOTICE: Vehicle will start and run after an extended crank with Code P012 set. This is because 24X reference pulses are being received by the PCM and the PCM can use this signal for fuel control instead.

Test Condition(s)

1. Codes P035 and P041 not set.
2. Code P012 is tested anytime the CAM sensor signals are being received.

Failure Condition(s)

If the PCM does not receive 4X reference pulses for 4 seconds while receiving CAM reference pulses, Code P012 will set.

Action Taken

1. PCM turns 'ON' the 'SERVICE ENGINE SOON' MIL.

Notes on Fault Tree

1. Check to see if Code P035 is set 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 the Electronic Ignition System. If the voltmeter reads 4.1 volts or greater, the Ignition Control Module is able to produce 4X reference pulses.
4. Checking to see if the Code P012 was set while the vehicle was running or not, if MAP value is 80 kPa or less vehicle was running at code set. Stray CAM pulses at key 'ON' engine not running can cause Code P012 to set falsely.
5. Checking for 4X reference pulses on CKT 430 from the Ignition Control Module to the PCM. If PCM terminal '3E2' has between 30 and 100 Hertz, the PCM is receiving 4X reference pulses.
6. Checking if a faulty PCM is pulling the 4X signal low.
7. Checking for short to voltage on CKT 430.
8. Checking if ICM is providing proper reference signal to PCM.