No Response From Controller Anti-Lock Brake
NOTE:
After making any repairs, perform CONTROLLER ANTI-LOCK BRAKE VERIFICATION TEST
under VERIFICATION TESTS.
- Connect scan tool to Data Link Connector (DLC), under lower left side of instrument panel. Turn ignition on. Select BODY, then BODY COMPUTER. If scan tool is able to identify or communicate with Central Timer Module (CTM) and/or Mechanical Instrument Cluster (MIC), go to next step. If scan tool is not able to identify or communicate with CTM and/or MIC, see PCI BUS COMMUNICATION FAILURE .
- Turn ignition off. Check fuse No. 27 (10-amp) in instrument panel junction block. Instrument panel junction block is located on left end of instrument panel. If fuse is okay, go to step 6 . If fuse is blown, go to next step.
- Install NEW 10-amp fuse No. 27 into instrument panel junction block. Turn ignition on. Remove and inspect fuse No. 27. If fuse No. 27 is blown, go to next step. If fuse No. 27 is okay, check ignition switch output circuit for intermittent short to ground. See POWER DISTRIBUTION article in WIRING DIAGRAMS. Repair as necessary.
- Turn ignition off. Install NEW 10-amp fuse No. 27 into instrument panel junction block. Disconnect Black 14-pin Controller Anti-Lock Brake (CAB) connector C1. See COMPONENT LOCATIONS . Turn ignition on. Remove and inspect fuse No. 27. If fuse is blown, go to next step. If fuse is okay, replace CAB. See appropriate ANTI-LOCK article in BRAKES.
- Turn ignition off. Disconnect Blue 15-pin instrument panel junction block connector C2. See Fig 1 . Using DVOM, measure resistance between ground and Black 14-pin CAB connector C1 terminal No. 4 (Red/Dark Blue wire). See Fig 2 . If resistance is 5 ohms or less, repair short to ground in Red/Dark Blue wire between Black 14-pin CAB connector C1 terminal No. 4 and fuse No. 27 in instrument panel junction block. If resistance is more than 5 ohms, replace instrument panel junction block.
- Using DVOM, measure resistance between ground and Black 14-pin CAB connector C1 terminals No. 6 and 13 (Black/Pink wires). See Fig 2 . If resistance is 5 ohms or less on both circuits, go to next step. If resistance is more than 5 ohms, repair open or high resistance in appropriate Black/Pink wire between Black 14-pin CAB connector C1 and ground. See GROUND DISTRIBUTION article in WIRING DIAGRAMS.
- Install fuse No. 27 into instrument panel junction block. Turn ignition on. Using test light connected to ground, probe Black 14-pin CAB connector C1 terminal No. 4 (Red/Dark Blue wire). If test light illuminates, go to next step. If test light does not illuminate, repair open in Red/Dark Blue wire between Black 14-pin CAB connector C1 terminal No. 4 and fuse No. 27 in instrument panel junction block. See POWER DISTRIBUTION article in WIRING DIAGRAMS.
- Ensure there is PCI BUS communication with other modules before proceeding. If there is no PCI BUS communication with other modules, perform appropriate test relating to no communication. See DIAGNOSTIC TROUBLE CODE IDENTIFICATION table under SELF-DIAGNOSTIC SYSTEM. Connect Scope Input Cable (CH7058) to channel one connector on scan tool. Connect Cable-To-Probe Adapter (CH7062) and Black and Red test probes to scope input cable. Connect Black test probe to ground. Connect Red test probe to PCI BUS circuit at Black 14-pin CAB connector C1 terminal No. 3 (Violet/Yellow wire).
- Using scan tool, select PEP MODULE TOOLS, LAB SCOPE, LIVE DATA. Select 12 VOLT SQUARE WAVE. Press F2 for SCOPE. Press F2 and use DOWN arrow to set voltage scale to 20 volts. Press F2 again when complete. Turn ignition on. If reading on lab scope toggles between zero and 7.5 volts, replace CAB. See appropriate ANTI-LOCK article in BRAKES. If reading on lab scope does not toggle between zero and 7.5 volts, repair open in PCI BUS circuit (Violet/Yellow wire).