Troubleshooting Hints - UART Data Line

PERFORM BEFORE BEGINNING SYSTEM DIAGNOSIS:
UART DATA LINE
1. If all components are not accessible with a scan tool, check for an open in CKT 800 between DLC terminal "9" and S277.

2. If a single component is not accessible with a scan tool, check for an open in CKT 800. If the wire is OK, refer to Antilock Brake System for ABS diagnosis, and to Air Bags (Supplemental Restraint Systems) for Supplemental Air Restraint diagnosis, and Instrument Panel, Gauges and Warning Indicators for Instrument Cluster diagnosis.
Antilock Brakes / Traction Control Systems
Restraints and Safety Systems
Instrument Panel, Gauges and Warning Indicators

OBDII DATA LINE
1. If PCM is not accessible with a scan tool, check for an open in CKT 1807. If the wire is OK, refer for Powertrain Control Module Diagnosis.
^ Check for a broken (or partially broken) wire inside of the insulation which could cause system failure but prove "GOOD" in a continuity/voltage check (refer to "General Troubleshooting Procedures,"). Diagnostic Aids
^ Check for proper installation of aftermarket electronic equipment which may affect the integrity of other systems (refer to "General Troubleshooting Procedures,").