2003 Chevrolet Impala LSFACTORY OEM SERVICE PROCEDURE

Test Description

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

  1. 5:  Listen for an audible click when the REAR DEFOG relay operates. Command both the ON and OFF states of the REAR DEFOG relay. Repeat the commands as necessary.
Defogger Inoperative - Rear Window

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
IMPORTANT: Make sure that the park or head lights are turned OFF. The backlighting will effect the illumination of the rear window defogger indicator.
  1. Start the engine.
  2. Depress the rear window defogger switch.
  3. Observe the rear window defogger indicator on the HVAC Control Module.
Does the rear window defogger indicator illuminate?		 Go to Step 3  Go to Step 12 
3 Connect a test lamp between the rear window defogger grid and a good ground.
Does the test lamp illuminate?		 Go to Step 4  Go to Step 5 
4 Connect a test lamp between the left side of the rear window defogger grid and the right side of the rear window defogger grid.
Does the test lamp illuminate?		 Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems Go to Step 19 
5  Command the REAR DEFOG relay ON and OFF, by depressing the rear defogger switch on the HVAC Control Module.
Do you hear a click when you command the REAR DEFOG relay ON and OFF?		 Go to Step 8  Go to Step 6 
6
  1. Turn OFF the ignition.
  2. Disconnect the REAR DEFOG relay.
  3. Start the engine.
  4. Connect a test lamp between the supply voltage circuit of the REAR DEFOG relay coil and a good ground.
Does the test lamp illuminate?		 Go to Step 7  Go to Step 11 
7
  1. Connect a test lamp between the supply voltage circuit of the REAR DEFOG relay coil and the control circuit of the REAR DEFOG relay.
  2. Depress the rear window defogger switch.
Does the test lamp illuminate?		 Go to Step 17  Go to Step 12 
8
  1. Turn OFF the ignition.
  2. Disconnect the REAR DEFOG relay.
  3. Connect a test lamp between the battery positive voltage circuit of the REAR DEFOG relay switched input and a good ground.
Does the test lamp illuminate?		 Go to Step 9  Go to Step 13 
9
  1. Connect a 30-ampere fused wire between the battery positive voltage circuit of the REAR DEFOG relay switched input and the relay switched output to the supply voltage circuit of the rear window defogger grid.
  2. Connect a test lamp between the rear window defogger grid and a good ground.
Does the test lamp illuminate?		 Go to Step 17  Go to Step 10 
10
  1. Disconnect the harness connector of the radio antenna module.
  2. Connect a test lamp between the supply voltage circuit of the rear window defogger grid and a good ground.
Does the test lamp illuminate?		 Go to Step 14  Go to Step 21 
11 Test the supply voltage circuit of the REAR DEFOG relay coil for an open or short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 26  Go to Step 16 
12 Test the control circuit of the REAR DEFOG relay for an open or short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 26  Go to Step 15 
13 Test the battery positive voltage circuit of the REAR DEFOG relay switched input for an open or short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 26  Go to Step 20 
14 Test the supply voltage circuit of the rear window defogger grid between the radio antenna module and the rear window defogger grid for an open or high resistance. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 26  Go to Step 18 
15 Inspect for a poor connection at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 26  Go to Step 22 
16 Inspect for a poor connection at the harness connector of the body control module (BCM). Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 26  Go to Step 23 
17 Inspect for a poor connection at the REAR DEFOG relay. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 26  Go to Step 24 
18 Inspect for a poor connection at the harness connector of the radio antenna module. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems.
Did you find and correct the condition?		 Go to Step 26  Go to Step 25 
19 Repair an open or high resistance in the ground circuit of the rear window defogger grid. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 26  -
20 Repair the short to ground in the supply voltage circuit of the rear window defogger grid. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 26  -
21 Repair an open or high resistance in the supply voltage circuit of the rear window defogger grid. Refer to Wiring Repairs in Wiring Systems.
Did you complete the repair?		 Go to Step 26  -
22 Replace the HVAC control module. Refer to HVAC Control Assembly Replacement in HVAC Systems - Manual.
Did you complete the replacement?		 Go to Step 26  -
23
IMPORTANT: Perform the setup procedure for the Body Control Module (BCM).
Replace the BCM. Refer to Body Control Module Replacement in Body Control System.Did you complete the replacement?		 Go to Step 26  -
24 Replace the REAR DEFOG relay.
Did you complete the replacement?		 Go to Step 26  -
25 Replace the radio antenna module. Refer to Antenna Module Replacement in Entertainment.
Did you complete the replacement?		 Go to Step 26  -
26 Operate the system in order to verify the repair.
Did you correct the condition?		 System OK Go to Step 2 
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