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 glass heating grid lines.

NOTE: For circuit descriptions and diagrams of the rear window defogger system, refer to 8W - WIRING DIAGRAM INFORMATION.

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

1. If equipped with the automatic temperature control (ATC) heating-A/C system, use a scan tool and check for diagnostic trouble codes (DTCs) related to the A/C-heater control. If equipped with the manual temperature control (MTC) heating-A/C system, use the A/C-heater control to check for diagnostic trouble codes (DTCs) related to the A/C-heater control (refer to 24 - HEATING & AIR CONDITIONING - DIAGNOSIS AND TESTING - HVAC SELF DIAGNOSTICS). 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. Turn the rear window defogger switch ON. Rear window defogger operation can be checked by feeling the surfaces of the rear window glass or outside rear view mirror glass. A distinct difference in temperature between the grid lines (5) or mirror glass and the adjacent clear 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 and contact the rear glass heating grid terminal A (1) with the negative lead, and terminal B (2) with the positive 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 (3) 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 (6) is connected to the heating grid negative terminal and that there is continuity to ground.
Check the EBL relay and fuse located in the junction block (JB) inside the vehicle and the fuse located in power distribution center (PDC) located in the engine compartment. The relay and both fuses must be tight in their receptacles and all electrical connections must be secure.

4. If broken rear defogger grid lines or bus bars are suspected, use a 12-volt DC voltmeter and contact terminal A 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).
5. If the EBL system still does not operate, replace the A/C-heater control (refer to 24 - HEATING & AIR CONDITIONING/CONTROLS/CONTROL-A/C HEATER - REMOVAL).
6. If operation of the EBL system has been verified, but both of the heated rear view mirrors do not produce heat, check the fuse for the heated mirror system located in the JB inside the vehicle.
7. If operation of the EBL system has been verified, but the rear window defogger LED indicator does not illuminate, replace the A/C-heater control (refer to 24 - HEATING & AIR CONDITIONING/CONTROLS/CONTROL-A/C HEATER - REMOVAL).