Quad-Driver Check (Except 3.1L)

Remove ECM from vehicle. Using DVOM on 100/200 k/ohm scale, measure resistance between ECM case and each ECM quad-driver terminal. Touch negative DVOM lead to case and positive lead to ECM terminal. See ECM QUAD-DRIVER TERMINAL IDENTIFICATION table.
Each terminal should have at least 50 k/ohms resistance. If all quad-driver terminals have greater than 50 k/ohms resistance, go to step 4). If any terminal has less than 50 k/ohms resistance, locate driven component(s) for the quad-driver with the lowest resistance. Disconnect component from circuit and check circuit for short to voltage.
If circuit is not shorted to voltage, replace component before replacing ECM to prevent recurring ECM failure. See appropriate ECM QUAD-DRIVER TERMINAL IDENTIFICATION table.
Using a fused ammeter capable of measuring at least 2 amps, turn ignition on with engine off. Connect one lead of ohmmeter to chassis ground. Connect remaining lead to each ECM harness quad-driver circuit. Measure each circuit for sustained current flow for at least 2 minutes.
NOTE: TCC solenoid cannot be easily tested for current draw, since completed circuit depends upon internal transmission oil pressure switches.
If no circuit has more than .75 amp sustained current flow, replace ECM. If any circuit has more than .75 amp sustained current flow, check for short to voltage in that circuit. If short to voltage is not present, replace related solenoid or relay.

ECM QUAD-DRIVER TERMINAL IDENTIFICATION (2.5L)

ECM QUAD-DRIVER TERMINAL ID 2.8L, 4.3L & V8 W/O 4L80-E TRANS)

ECM QUAD-DRIVER TERMINAL ID (4.3L & V8 WITH 4L80-E TRANS)