Chart 7 Improper Rear Defogger Operation

Rear Defogger Schematic:

Chart 7, Rear Defogger On Continuously:

CIRCUIT DESCRIPTION
The Electronic Climate Control (ECC) programmer provides a ground for the defogger relay when it receives a command from the climate control center via the data line and Body Control Module (BCM). The BCM times the operation initially for 10 minutes, then commands the programmer to deactivate the relay ground. Additional requests for rear defogger are for 5 minute intervals, thereafter until a new ignition cycle occurs.

1. This step eliminates a short to voltage on Circuits 293 or 676.
2. This step checks the relay switch resistance. A closed relay switch can cause this condition.
3. This step distinguishes between a short to ground on Circuit 291 and a faulty ECC programmer.