With CRT/DID

CIRCUIT DESCRIPTION
With a grounded serial data circuit the BCM will not be able to communicate with any other devices in the system. Voltage measured anywhere along the circuit will be zero. The display on the IPC will be "ELECTRICAL PROBLEM" and the CRT/DID will display normally, but HVAC controls will not function.

TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart.
1. This step splits the system in half to help isolate the source of the grounded serial data line. If taking the PCM out of the system allows both halves of serial data line to rise above 1 volt the source of the short has been located.

The remaining steps follow the same pattern in that the components are removed from the serial data line until the normal voltage range is again measured. When the section of the circuit is isolated a simple check of the wire for a short to ground differentiates between a grounded wire or a ground in the device remote.