The rear defogger switch is a momentary switch to ground. The intelligent switching unit (ISU) monitors the status of the rear defogger switch. The ISU energizes the internal rear defogger relay when it detects a change of status in the rear defogger switch. The ISU de-energizes the internal rear defogger relay when it detects the next change of status in the rear defogger switch or a predetermined on time interval has elapsed.
The ignition is ON.
The ISU detects a high voltage level on the rear defogger switch circuit for 2 seconds.
The rear window defogger will be disabled until the condition is no longer present.
• | The ISU no longer detects a high voltage level on the rear defogger switch circuit. |
• | A history DTC will clear after 40 consecutive ignition cycles if the condition for the malfunction is no longer present. |
The numbers below refer to the step numbers on the diagnostic table.
This step tests the inactive state of the rear defogger switch.
This step tests the active state of the rear defogger switch.
After replacement of the ISU, the ISU must be reprogrammed.
Step | Action | Yes | No |
---|---|---|---|
Schematic Reference: Defogger Schematics Connector End View Reference: Component Connector End Views | |||
1 | Did you perform Diagnostic System Check - Vehicle? | Go to Step 2 | |
Does the scan tool display OFF? | Go to Step 3 | Go to Step 6 | |
Important: The rear defrost switch parameter is a momentary display. Observe the scan tool carefully. Does the rear defrost switch parameter change state? | Go to Step 13 | Go to Step 4 | |
4 |
Is the fuse open? | Go to Step 5 | Go to Step 8 |
5 |
Is the repair complete? | Go to Step 13 | -- |
6 |
Does the scan tool display OFF? | Go to Step 10 | Go to Step 7 |
7 | Test the signal circuit of the defogger switch for a short to ground. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 8 |
Test the signal circuit of the defogger switch for a short to voltage. Refer to Circuit Testing and Wiring Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 11 | |
9 | Inspect for poor connections at the harness connector of the intelligent switching unit (ISU). Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 11 |
10 | Inspect for poor connections at the harness connector of the defogger switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | Go to Step 13 | Go to Step 12 |
11 |
Important: Perform the program procedure for the ISU. Replace the ISU. Did you complete the replacement? | Go to Step 13 | -- |
12 | Replace the defogger switch. Did you complete the replacement? | Go to Step 13 | -- |
13 |
Does the DTC reset? | Go to Step 2 | System OK |