Chart D-1, Grounded Serial Data Circuit (CRT Equipped)

With grounded serial data circuit, BCM will not be able to communicate with any other devices in system. Voltage measured anywhere in circuit will be zero. IPC display will show ELECTRICAL PROBLEM, CRT will display normally and HVAC controls will not function.

1. This step splits system in half to help isolate source of grounded serial data line. If taking PCM out of system allows both halves of serial data line to rise to greater than one volt, source of short has been located. Remaining steps follow same pattern, as components are removed from serial data line until normal voltage range is again measured. When section of circuit is isolated, a simple check of wire for short to ground will differentiate between grounded wire or ground in a device remote.

Fig 1: Chart D-1, Schematic, Grounded Serial Data Ckt (CRT Equipped)

Fig 2: Flow Chart D-1 Grounded Serial Data Ckt (CRT Equipped)