• | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
• | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
• | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
---|---|---|---|---|
Liftgate Module B+ | 2 | 2 | -- | -- |
Rear Defog Grid Control | B0283 | B0283 | 1 | -- |
Rear Window Defogger Grid Ground | -- | 2 | 2 | -- |
1. Rear defogger always ON 2. Rear defogger Inoperative |
The rear window defogger switch and indicator is an integral component of the HVAC control module. When the rear window defogger switch is pressed, the HVAC control module responds by illuminating the defogger indicator and sending a serial data message indicating a defog request. This serial data message is received by the liftgate module (LGM). The LGM responds to the defog request by providing voltage to the rear window defogger grid. Pressing the rear window defogger switch again will turn off the indicator and send a serial data message indicating the defog deactivation command. The LGM responds by deactivating the defogger grid.
Rear Window Defogger Description and Operation
Control Module References for scan tool information
⇒ | If the parameter does not change between commanded states, replace the HVAC control module. |
⇒ | If the indicator does not turn ON or OFF with each switch press, replace the HVAC control module |
⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the LGM #2 fuse is open, replace the LGM. |
⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the LGM. |
⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the LGM. |
⇒ | If the test lamp remains bright at the middle of the grid line, test for an open between the test point and the ground side of the grid. |
⇒ | If the test lamp remains off at the middle of the grid line, test for an open between the test point and the voltage supply side of the grid. |
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
• | Control Module References for HVAC control module and LGM replacement, setup, and programming |