No Response From CAB
NOTE:
After making any repairs, perform ANTI-LOCK BRAKE SYSTEM VERIFICATION TEST under VERIFICATION TESTS.
- Turn the ignition on. With the DRBIII, attempt to communicate with the Airbag Control Module (ACM). With the DRBIII, attempt to communicate with the Instrument Cluster (MIC). If the DRBIII was able to I/D or establish communications with either of the modules, go to the next step. If the DRBIII was not able to I/D or establish communications with either of the modules, see PCI BUS COMMUNICATION FAILURE .
- Turn the ignition off. Disconnect the CAB harness connector. See Fig 1. Using a 12-volt test light connected to 12 volts, probe both ground circuits. If the test light illuminated for both circuits, go to the next step. If the test light did not illuminate, repair the ground circuits for an open.
- Turn the ignition off. Disconnect the CAB harness connector. Turn the ignition on. Using a 12-volt test light connected to ground, probe the fused ignition switch output circuit. If the test light illuminated, go to the next step. If the test light did not illuminate, repair the fused ignition switch output circuit for an open.
- Disconnect the CAB harness connector. Use Scope Input Cable (CH7058), Cable-To-Probe Adapter (CH7062), and the Red and Black test probes. Connect the Scope Input Cable to the channel one connector on the DRBIII. Attach the Red and Black leads and the Cable-To-Probe Adapter to the Scope Input Cable. With the DRBIII select PEP MODULE TOOLS. Select LAB SCOPE. Select LIVE DATA. Select 12 VOLT SQUARE WAVE. Press F2 for scope. Press F2 and use the down arrow to set voltage range to 20 volts. Set Probe to x10. Press F2 again when complete. Connect the Black lead to the chassis ground. Connect the Red lead to the PCI bus circuit in the CAB connector. Turn the ignition on. Observe the voltage display on the DRBIII lab scope. If the voltage pulses from 0 to approximately 7.5 volts, go to the next step. If the voltage does not pulse from 0 to approximately 7.5 volts, repair the PCI bus circuit for an open.
- If there are no possible causes remaining, replace the controller antilock brake. See appropriate ANTI-LOCK article in BRAKES.
NOTE:
Ensure there is PCI Bus communication with other modules on the vehicle before proceeding. If not, refer to the symptom index from the menu and repair as necessary. See SYMPTOM INDEX table under SELF-DIAGNOSTIC SYSTEM.