Troubleshooting Hints - Exterior Lights
^ The CHMSL Resistor has been added to the circuit to control the intensity level of the High Mounted Stop Lamp. If this 510 ohm resistor opens, a greater amount of current flows through the CHMSL and will exceed intensity levels specification. Should this problem exist on a vehicle, check for voltage and ground at the CHMSL Resistor and repair any open circuit. If the 510 ohms CHMSL Resistor is open, replace as necessary1. CHECK condition of TURN-B/U, STOP/HAZ, PK LPS, and UPFIT-BATT Fuse(s). If Fuse(s) is open LOCATE and REPAIR cause of overload and REPLACE Fuse.
2. CHECK that Ground(s) G100, G101, G105, G110, G400 and G401 are clean and tight.
3. For Diagnosis of the Backup Lamps, Refer to Backup Lamp. Backup Lamp
4. If Stoplamps and Hazard Flashers do not operate, CHECK for a short to ground or open in ORN (140) wire between I/P Fuse Block and Splice S225
5. If a Single Lamp does not operate, CHECK the Bulb, Socket and Lamp ground wire.
6. Any inoperative Trailer Tow Wire should be checked from that Terminal to the appropriate Splice.
^ 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 system (See Diagnostic Aids for General Troubleshooting Procedures). Diagnostic Aids