Component Tests and General Diagnostics

ELECTRIC BACKLIGHT (EBL) SYSTEM

NOTE: Illumination of the defogger switch indicator lamp does not necessarily mean that electrical current is reaching the rear glass heating grid lines.

NOTE: For circuit descriptions and diagrams of the rear window defogger (EBL) system, refer to WIRING DIAGRAM INFORMATION.





Operation of the electrical backlight (EBL) system can be confirmed by the following:

1. Use a scan tool and check for diagnostic trouble codes (DTCs) related to the A/C-heater control and the body control module (BCM). If no DTCs are found, go to STEP 2. If any DTCs are found, repair as required, then proceed to STEP 2.
2. Turn the ignition switch to RUN. Set the rear window defogger switch to ON. Rear window defogger operation can be checked by feeling the rear window glass (1). A distinct difference in temperature between the grid lines (2) and the adjacent clear glass should be detected within three to four minutes of operation.
3. If a temperature difference is not detected, use a 12-volt DC voltmeter (5) and contact the rear glass heating grid power feed terminal (4) with the positive lead, and the ground terminal (8) with the negative lead. The voltmeter should read battery voltage. If the voltmeter does not read battery voltage, check the following:
- Confirm the ignition switch is in RUN.
- Confirm the rear window defogger switch is ON.
- Confirm the EBL feed wire is connected to the heating grid positive terminal and that there is continuity between the EBL relay and the heating grid.
- Confirm the EBL ground wire is connected to the heating grid negative terminal and that there is continuity to ground.
- Check the EBL relay and fuse located in the power distribution center (PDC). The relay and fuse must be tight in their receptacles and all electrical connections must be secure.

4. If broken defogger grid lines or bus bars (3) are suspected, use a 12-volt DC voltmeter and contact the ground terminal with the negative lead and each rear glass heating grid line at its mid-point (6) with the positive lead. The voltmeter should read approximately 6 volts at each grid line mid-point. If the voltmeter does not read approximately 6 volts, repair the open grid line(s) or bus bar(s) Service and Repair.
5. If EBL system operation has been verified but the rear window defogger indicator does not illuminate, replace the A/C-heater control A/C Heater Control - Removal.