DIAGNOSIS AND TESTING

ELECTRIC BACKLIGHT (EBL) SYSTEM

NOTE: Illumination of the defogger switch indicator lamp does not necessarily mean that electrical current is reaching the rear window glass and/or the outside rear view mirror heating grids (when equipped).

NOTE: For circuit descriptions and diagrams of the rear window defogger (EBL) and heated mirror systems, refer to 8W - WIRING DIAGRAM INFORMATION.

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

NOTE: Typical heated rear window glass shown.

1. Use a scan tool and check for diagnostic trouble codes (DTCs) related to the rear window defogger switch, cabin compartment node (CCN) and the totally integrated power module (TIPM). 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), or the heated outside rear view mirror glass when equipped with heated mirrors. A distinct difference in temperature between the grid lines (2) and the adjacent clear glass or the heated mirror glass should be detected within 3 to 4 minutes of operation.
3. If a temperature difference is not detected, use a 12-volt DC voltmeter (6) and contact the rear glass heating grid terminal A (5) with the positive lead, and terminal B (7) 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 TIPM and the heating grid.
Confirm the EBL ground wire is connected to the heating grid negative terminal and that there is continuity to ground.
When diagnosing a heated mirror concern, check the heated mirror circuit fuse located in the TIPM. The fuse must be in the receptacle 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 terminal B with the negative lead and each rear glass heating grid line at its mid-point C (4) 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) (refer to 8 - ELECTRICAL/HEATED GLASS/GRID-REAR WINDOW DEFOGGER - STANDARD PROCEDURE - GRID LINE AND TERMINAL REPAIR).
5. If EBL system operation has been verified but the rear window defogger indicator does not illuminate, replace the A/C-heater control (refer to 24 - HEATING & AIR CONDITIONING/CONTROLS/CONTROL-A/C HEATER - REMOVAL).