Initial Inspection and Diagnostic Overview

1. Check the CIGAR/Data Link Connector (DLC) Fuse for an open. If the fuse is blown check CKT 440 for a short to ground.
2. Make sure that G200 is clean and tight.
3. If all components (except Radio) are not accessible with a Scan Tool, check for an open in the UART Serial Data Line (CKT 800) between the Data Link Connector terminal "9" and S237. If the wires are OK, refer to ABS diagnosis and to Supplemental Air Restraint diagnosis. Air Bag Systems
4. If the Radio is not accessible with a Scan Tool, check for an open in the Entertainment and Comfort Serial Data Line (CKT 835) between the Data Link Connector terminal "14" and the Radio.
5. If the Powertrain Control Module (PCM) is not accessible with a Scan Tool, check the Class II Serial Data Line between the Data Link Connector terminal "2" and the PCM. Also check C101 for a poor connection. If the wires are OK, refer to Engine Controls for PCM diagnosis. 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.