PD17: Fault EFGH

PCM Output Fault Status B. The PCM contains chips, called quad drivers that provide four switchable ground outputs for running solenoids, relays, telltales and the like. Each of these chips has a fault line that feeds back to the PCM's microprocessor. Each quad driver watches its four output lines.

When the output is "OFF", it should see the 12 volts fed to the solenoid, relay coil, or telltale on its output and when the output is on, it should see 0 volt since it is grounding the output. If it sees 0 volt when its output is "OFF" or 12 volts when its output is on it pushes the fault line high.

Other PCM outputs use individual transistors to drive things like injectors or the generator enable. The PCM can monitor these circuits to check for faults the same as the quad drivers do. PCM Output Fault Status B shows the states of fault lines from one PCM quad driver the eight injector drivers and the generator enable circuit. Each quad driver corresponds to one digit of the display and each digit can only appear as "0" or "1". A "0" means that no output faults are present. A "1" means that a fault is present on at least one output of that quad driver. QUAD DRIVER IDENTIFICATION CHART 2  below identifies the quad drivers corresponding to each digit and what is driven by that driver: