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Test Description

The number below refers to the step number on the diagnostic table.

  1. 3:  Command both the ON and OFF states of the rear window defogger switch. Repeat the command as necessary to verify the Rear Defog Switch Input data parameter does or doesn't change states.
Defogger Indicator Always On

Step Action Yes No
Schematic Reference: Defogger Schematics 
Connector End View Reference: Stationary Windows Connector End Views 
1 Did you perform the Defogger Diagnostic System Check? Go to Step 2  Go to Diagnostic System Check - Defogger 
2
  1. Turn ON the ignition, with the engine OFF.
  2. Observe the rear window defogger indicator on the HVAC Control Assembly.
  3. Command the rear window defogger indicator ON and OFF, by depressing the rear window defogger switch.
Does the rear window defogger indicator turn ON and OFF with each command?		 Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems Go to Step 3 
3 
  1. Install a scan tool.
  2. With the scan tool, observe the Rear Defog Switch Input Data parameter in the Body Control Module (BCM) HVAC data list.
  3. Depress the rear window defogger switch.
Does the Rear Defog Switch Input Data parameter always display On?		 Go to Step 4  Go to Step 5 
4
  1. Turn OFF the ignition.
  2. Disconnect harness connector C4 of the BCM.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp from the rear window defogger switch signal circuit to battery voltage.
Does the test lamp illuminate?		 Go to Step 6  Go to Step 7 
5
  1. Turn OFF the ignition.
  2. Disconnect harness connector C3 of the BCM.
  3. Turn ON the ignition, with the engine OFF.
  4. Connect a test lamp from the supply voltage circuit of the REAR DEFOG relay coil to a good ground.
Does the test lamp illuminate?		 Go to Step 9  Go to Step 10 
6 Test the rear defogger switch signal circuit of the HVAC control assembly for short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 13  Go to Step 8 
7 Inspect for poor connections at the harness connector of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 13  Go to Step 11 
8 Inspect for poor connections at the harness connector of the HVAC control assembly. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 13  Go to Step 12 
9 Repair a short to voltage in the supply voltage circuit of the REAR DEFOG relay coil. Refer toWiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 13  -
10 Repair a short to voltage in the supply voltage circuit of the rear window defogger indicator. Refer toWiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 13  -
11
IMPORTANT: Perform the programming or set up procedure for the control module if required.
Replace the BCM. Refer to Body Control Module Replacement in Body Control System.Did you complete the replacement?		 Go to Step 13  -
12 Replace the HVAC control assembly. Refer to HVAC Control Assembly Replacement in HVAC Systems - Manual.
Did you complete the replacement?		 Go to Step 13  -
13 Operate the system in order to verify the repair.
Did you correct the condition?		 System OK Go to Step 2 
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