PD16: Fault ABCD

PCM Output Fault Status A. 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. PCM Output Fault Status A shows the states of fault lines from four of the PCM's quad drivers. 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 1 below identifies the quad drivers corresponding to each digit and what is driven by that driver:

QUAD DRIVER IDENTIFICATION CHART 1

Quad Driver

Outputs Driven

A (1st Digit)

TCC Solenoid & Engine Temperature Light ⁽¹⁾

B (2nd Digit)

Pass Key®, Starter Inhibit Output, EGR & EVAP Solenoids ⁽¹⁾

C (3rd Digit)

Cooling Fan Relays & "Service Engine Soon" MIL

D (4th Digit)

A/C Clutch Relay, TCS Delivered Torque & RSS Lift/Dive Outputs ⁽¹⁾

⁽¹⁾	These quad drivers have one or more unused outputs. Their fault status lines will always be high whether or not a true failure is present.