Test A - Power Interruption
- Perform ABS/TCS functional check before proceeding. See Figure
. Turn ignition switch to OFF position. Disconnect ABS main relay. ABS main relay is third from right in underhood fuse block. Using DVOM, measure voltage between ABS main relay connector terminal No. 87 (Red wire) and ground. See Fig 1
.
- Ensure battery voltage is present. If battery voltage is present, go to next step. If battery voltage is not present, check fuse No. 2 (30A) in left underhood fuse block, circuit No. 342 (Red wire) and circuit No. 1633 (Red wire) for open or short to ground. If circuit No. 1633 (Red wire) is shorted to ground, replace ABS main relay after repairing wire.
- Turn ignition switch to RUN position. Measure voltage between ABS main relay connector terminal No. 86 (Brown wire) and ground. See Fig 1
. Battery voltage should be present. If battery voltage is present, go to next step. If battery voltage is not present, check circuit No. 641 (Brown wire) for open.
- Measure resistance between ABS main relay terminals No. 85 and 86. See Fig 1
. Resistance should be 45-90 ohms. If resistance is as specified, go to TEST B. If resistance is not as specified, replace ABS main relay. After all repairs are complete, clear codes, and repeat ABS/TCS functional check. See Figure
.
Courtesy of GENERAL MOTORS CORP.