Rear Defogger: Testing and Inspection

ELECTRIC BACKLIGHT (EBL) SYSTEM

NOTE:
- Illumination of the defogger switch indicator lamp does not necessary mean that electrical current is reaching the rear glass heating grid lines.
- For circuit descriptions and diagrams of the rear window defogger (EBL) system, refer to WIRING DIAGRAM INFORMATION.

Operation of the electric backlight (EBL) system can be confirmed by the following:
1. Use a DRBIII(R) scan tool and check for diagnostic trouble codes (DTCs) related to 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 the On position. Set the rear window defogger switch in the On position. The 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 and the adjacent clear glass or the mirror glass should be detected within three to four minutes of operation.

Rear Window Glass Grid Test (Typical):

3. If a temperature difference is not detected, use a 12-volt DC voltmeter and contact the rear glass heating grid power feed terminal A with the positive lead, and the ground terminal B with the negative lead. The voltmeter should read battery voltage. If the voltmeter does not read battery voltage, check the following:
- Confirm that the ignition switch is On.
- Make sure that the rear glass heating grid feed wire and ground wire are connected to the terminals. Confirm that the ground wire has continuity to ground.
- Check the EBL relay and fuse located in the junction block (JB) in the passenger compartment. Check the fuse in the power distribution center (PDC) located in the engine compartment. The relay and fuses must be tight in their receptacles and all electrical connections must be secure. Refer to the appropriate wiring information for diagnosis and testing of the ISO-standard relay.
When the above steps have been completed and the rear glass heating grid is still inoperative, one or more of the following is faulty:
- Rear window defogger switch in the A/C-heater control.
- Rear window defogger timing circuitry in the body control module (BCM).
- Rear window defogger grid lines (all grid lines would have to be broken, or the power feed or the ground wire disconnected, for the entire heating grid to be inoperative).
4. If the EBL system operation has been verified but the rear window defogger LED indicator does not illuminate, check fuse 29 in the JB. If the fuse is OK, replace the A/C-heater control.