Initial Inspection and Diagnostic Overview

PERFORM BEFORE BEGINNING SYSTEM DIAGNOSIS
1. If all components are not accessible with a scan tool, check for an open in PPL wire between S249 and DLC-OBD II.
2. If a single component is not accessible with a scan tool, check for an open in PPL or PPL/WHT wire between component and S249. If the wire is OK, refer to Antilock Brakes / Traction Control Systems for ABS diagnosis and Air Bag Systems for Supplemental Inflatable Restraint (SIR) diagnosis.
Check for an open (or partially broken) wire inside of the insulation which could cause system malfunction but prove "GOOD" in a continuity/ voltage check with the 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 (see "Troubleshooting Procedures", Diagnostic Aids

^ Refer to System Diagnosis. System Diagnosis