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• When Monitored: • Continuously. • Set Condition: • Whenever the Can B Bus (+) or B Bus (–) circuit is open, shorted to voltage or shorted to ground, this code Possible Causes CAN B BUS DTCs IN FRONT CONTROL MODULE (D54) CAN B BUS (–) CIRCUIT OPEN (D55) CAN B BUS (+) CIRCUIT OPEN AMPLIFIER Diagnostic Test 1. TEST FOR INTERMITTENT CONDITION Turn the ignition on. With the scan tool, record and erase DTCs Cycle the ignition from on to off 3 times. Turn the ignition on. With the scan tool, read DTCs. Does the scan tool display U0020-CAN B BUS OFF PERFORMANCE? Yes >> Go To 2 No >> The conditions that caused this code to set are not present at this time. Using the wiring diagram/sche- matic as a guide, inspect the wiring and connectors. Perform BODY VERIFICATION TEST - VER 1. 2. CHECK FRONT CONTROL MODULE DTCs With the scan tool, read Front Control Module DTCs Does the scan tool display any CAN B BUS DTCs – ACTIVE? Yes >> Refer to the symptom list for problems related to Communication in the ELECTRICAL.– ELECTRONIC CONTROL MODULES – ELECTRICAL DIAGNOSES section. No >> Go to 3 3. CAN B BUS (+) CIRCUIT OPEN Turn the ignition off. Disconnect the Amplifier harness connector. Disconnect the Front Control Module C1 harness connector. Measure the resistance of the (D55) Can B Bus (+) circuit between the Front Control Module C1 harness connector Is the resistance below 2.0 ohms? Yes >> Go To 4 Perform BODY VERIFICATION TEST - VER 1. No >> Repair the Can B Bus (+) circuit for an open. Perform BODY VERIFICATION TEST - VER 1. 8A - 94 AUDIO - ELECTRICAL DIAGNOSTICS LX |