DTC P1687: No Cluster Bus Message: Testing

Turn ignition the on. With the DRBIII®, erase DTCs. Cycle the ignition key on and off several times leaving the ignition in the ON position for a minimum of 20 seconds each time. With the DRBIII®, read DTCs. Does the DTC reset? If yes, go to next step. If no, go to step 4.
With the DRBIII®, attempt to communicate with the Instrument Cluster. Can communication be established with the Instrument Cluster? If yes, go to next step. If no, diagnose communication fault. See COMMUNICATIONS under SYSTEM TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
Start the engine. Allow the engine to idle. Is the correct engine speed displayed in the instrument cluster (Tach)? If yes, replace PCM. Program the new PCM. See PROGRAMMING . If no, repair instrument cluster problem. See INSTRUMENT CLUSTER SYSTEMS under SYSTEM TESTS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.

WARNING: When the engine is operating, do not stand in a direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing.

The conditions that set the DTC are not present at this time. The following may help in identifying the intermittent condition. With the engine running at normal operating temperature, monitor the DRBIII® parameters related to the DTC while wiggling the wiring harness. Look for parameter values to change and/or a DTC to set. Review the DRBIII® Freeze Frame information. If possible try to duplicate the conditions under which the DTC was set. Refer to any Technical Service Bulletins (TSB) that may apply. Visually inspect the related wiring harness. Look for any chafed, pierced, pinched, or partially broken wires. Visually inspect the related wiring harness connectors. Look for broken, bent, pushed out, or corroded terminals. Were any of the above conditions present? If yes, repair as necessary. If no, test is complete.