Bus +/- Signal Open From Body Control Module (BCM)
- Turn ignition on. Using scan tool, attempt to communicate with Air Bag Control Module (ACM) and Controller Anti-Lock Brake (CAB). If scan tool communicates with ACM and CAB, go to next step. If scan tool does not communicate with ACM or CAB, go to PCI BUS COMMUNICATIONS FAILURE . Perform BODY VERIFICATION TEST under VERIFICATION TESTS.
- Turn ignition off. Disconnect BCM connector C1. See Figure. Using DVOM, measure resistance between ground and BCM connector C1 terminal No. 1 (Black/Orange wire). See Fig 1. If resistance is less than 10 ohms, go to next step. If resistance is greater than 10 ohms, repair open in Black/Orange wire between BCM and ground. Perform BODY VERIFICATION TEST under VERIFICATION TESTS.
- Use Scope Input Cable (CH7058), Cable-To-Probe Adapter (CH7062) and Red and Black test probes. Connect scope input cable to channel one connector on scan tool. Attach Red and Black test probes and cable-to-probe adapter to scope input cable. Select scan tool STANDALONE function. Select LAB SCOPE. Select LIVE. Select 12 VOLT SQUARE WAVE. Press F2 for scope display. Press F2 and use down arrow to select voltage range to 20 volts. Press F2 after selecting 20 volts. Connect Black test probe lead to ground and Red test probe lead to BCM connector C1 terminal No. 15 (Yellow/Violet wire). Turn ignition on. Observe voltage readings on scan tool. If reading pulses from zero to approximately 7.5 volts, go to next step. If reading is steady at zero volts, repair PCI bus circuit (Yellow/Violet wire) between BCM and diagnostic junction port. See appropriate wiring diagram in DATA LINK CONNECTORS article in WIRING DIAGRAMS. Perform BODY VERIFICATION TEST under VERIFICATION TESTS.
- Replace BCM. See BODY CONTROL MODULE under REMOVAL & INSTALLATION. Perform BODY VERIFICATION TEST under VERIFICATION TESTS.
Courtesy of DAIMLERCHRYSLER CORP.