Initial Inspection and Diagnostic Overview

PCM DATA LINE
1. Check FUSE 10 for an open.
2. Check that G201 is clean and tight.
3. If all components (except Theft Deterrent Module) are not accessible with a Scan Tool, check for an open in CKT 800 between DLC terminal "9" and S237.
4. If the Theft Deterrent Module is not accessible with a Scan Tool, check for an open in CKT 728 between DLC terminal "8" and the Theft Deterrent Module.
5. If a single component is not accessible with a Scan Tool, check the UART Serial Data Line for an open in CKT 800 between S237 and the component. Check the Class 2 Serial Data Line between the Data Link Connector terminal "2" and the PCM. Also check C100 for a poor connection. If the wires are OK, refer to Antilock Brake System for ABS diagnosis and to Air Bags (Supplemental Restraint Systems) for Supplemental Air Restraint diagnosis.
Antilock Brakes / Traction Control Systems
Testing and Inspection
6. Always check terminal contact before replacing any component.
^ Check for a broken (or partially broken) wire inside of the insulation which could cause system malfunction but prove "GOOD" in a continuity/voltage check with a system disconnected. These circuits may be intermittent or resistive when loaded, and if possible, should be checked by monitoring for a voltage drop with the system operational (under load).
^ Check for proper installation of aftermarket electronic equipment which may affect the integrity of other systems (refer to General Troubleshooting Procedures). Diagnostic Aids
^ Refer to System Diagnosis.