How Do I Fix P1351 Ignition Coil Control 1999 gmc sierra Circuit High Voltage?


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Code P1351 Ignition Control (IC) Circuit High Voltage
Swap out your coil first to test.
This diagnostic will set when the following conditions are met:
Voltage on IC circuit is greater than 4.9 volts and engine speed is less than 250 RPM.
Basically the engine is either at rest or cranking when the VCM (PCM) is monitoring for the high voltage diagnstic.
The PCM has an internal 5 volt reference that's used for several circuits. This voltage is dropped across a resistor and fed to the corresponding control circuit. The BCM monitors this voltage to determine circuit integrity.
You could have a wiring problem between the PCM (ICU) and BCM, or a problem with the connector(s) at either the PCM or BCM, or the BCM is going bad.
For this problem a wiring diagram is your friend. You can check the connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal-to-wire connection, or rubbed through wire(s).
Check the PCM to BCM wiring very close.
A good way to find a wiring problem is to clear the code. Monitor the reference voltage while having someone pull on wiring at the BCM/PCM and wiggling the harnesses. If this makes the voltage to go high you know it's a wiring problem. If the voltage remains constant and the code RESETS than the VCM is the problem.

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