Class 2 Serial Data Line
- If all components are not accessible with a scan tool, check for an open in circuit 1807 or a short to battery or ground. See Figure . If the wire is good, see OBD DIAGNOSTIC SYSTEM CHECK in appropriate BASIC TESTING article.
- Visually inspect for obvious signs of mechanical and electrical damage. Inspect for blown fuses and damaged relays. Inspect for loose or corroded connections, damaged wiring harnesses and/or switches. Check for a broken or partially broken wire inside insulation, which could cause system malfunction but prove good in a continuity/voltage check with system disconnected. These circuits may be intermittent or resistive when loaded and should be checked by monitoring the voltage drop with the system under load.
- Ensure any aftermarket electronic equipment is properly installed. If fault is found, repair as necessary.