Information Bus: Testing and Inspection

VEHICLE COMMUNICATION






The PCI Bus Failure modes are broken down into two categories. Complete PCI Bus Communication Failure and individual module no response. Causes of a complete PCI Bus Communication Failure include a short to ground or battery on the PCI circuit. Individual module no response can be caused by an open circuit at the module, or an open battery or ground circuit to the affected module.

Symptoms of a complete PCI Bus Communication Failure would include but are not limited to:
* All gauges on the MIC stay at zero
* All telltales on MIC illuminate
* MIC backlighting at full intensity
* No response received from any module on the PCI bus (except PCM)
* No start (if equipped with Sentry Key Immobilizer)

Symptoms of individual module failure could include any one or more of the above. The difference would be that at least one or more modules would respond to the DRBIII.

Diagnosis starts with symptom identification.

If a complete PCI Bus Communication Failure is suspected, begin by identifying which modules the vehicle is equipped with and then attempt to get a response from the module with the DRBIII.

If any modules are responding, the failure is not related to the total bus, but can be caused by one or more modules, PCI circuit or power supply and ground circuits. The DRB III may display "BUS ± SIGNAL OPEN" or "NO RESPONSE" to indicate a communication problem.

These same messages will be displayed if the vehicle is not equipped with that particular module. The CCD error message is a default message used by the DRBIII and in no way indicates whether or not the PCI Bus is operational. The message is only an indication that a module is either not responding or the vehicle is not equipped.

NOTE: Communication over the BUS is essential to the proper operation of the vehicles on-board diagnostic systems and the DRBIII. Problems with the operation of the BUS or DRBIII must be corrected before proceeding with diagnostic testing. If there is a problem, refer to the communications category.

Refer to the appropriate diagnostic procedures for details on how to diagnose these faults using a DRB III scan tool.

Refer to the Body Control System Body Control Modulefor further Diagnostics.