GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

SCHEMATIC REFERENCE: Defogger Schematics

1

Did you perform A Diagnostic System Check - Defogger?

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Go to Step 2

Go to Diagnostic System Check - Defogger

2

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, monitor the rear defogger relay in the RIM control module, while pressing the rear defogger button on the heater and A/C control.

Does the scan tool indicate that the parameter switched

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Go to Step 3

Go to Step 12

3

With a scan tool, command the rear defogger relay ON and OFF.

Does the rear defogger relay click ON and OFF with each command?

--

Go to Step 9

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the rear defogger relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the coil side feed circuit of the rear defogger relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

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Go to Step 5

Go to Step 15

5

  1. Connect a test lamp between the rear defogger relay control circuit of the rear defogger relay and the coil side feed circuit of the rear defogger relay.
  2. With a scan tool, command the rear defogger relay ON and OFF .

Does the test lamp turn ON and OFF with each command?

--

Go to Step 13

Go to Step 6

6

Does the test lamp remain illuminated with each command?

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Go to Step 8

Go to Step 7

7

Test the rear defogger relay control circuit for a short to voltage or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 15

Go to Step 14

8

Test the rear defogger relay control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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Go to Step 22

Go to Step 14

9

Test the rear defogger fuse.

Is the fuse open?

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Go to Step 16

Go to Step 10

10

  1. Connect a test lamp between the rear defogger element supply voltage terminal and a good ground.
  2. Command the rear defogger relay ON and OFF.

Does the test lamp illuminate with each command?

--

Go to Step 11

Go to Step 19

11

  1. Turn OFF the ignition.
  2. Measure the resistance of the rear defogger element ground terminal to ground.

Is the resistance within the specified value?

1-3 ohms

Go to Step 17

Go to Step 18

12

Inspect for poor connections at the heater and A/C control. 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 22

Go to Step 20

13

Inspect for poor connections at the rear defogger relay. 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 22

Go to Step 19

14

Inspect for poor connections at the harness connector of the RIM. 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 22

Go to Step 21

15

Repair the coil side feed circuit of the rear defogger relay. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 22

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16

Repair the rear defogger element supply voltage circuit and replace the fuse.

Did you find and correct the condition?

--

Go to Step 22

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17

Repair open rear defogger element. Refer to Grid Line Repair .

Did you find and correct the condition?

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Go to Step 22

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18

Repair open rear defogger element ground circuit.

Did you find and correct the condition?

--

Go to Step 22

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19

Replace the rear defogger relay. Refer to Defogger Relay Replacement .

Did you complete the replacement?

--

Go to Step 22

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20

Replace the heater and A/C control. Refer to Control Assembly Replacement in HVAC.

Did you complete the replacement?

--

Go to Step 22

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21

Replace the RIM. Refer to Rear Integration Body Control Module Replacement .

Did you complete the replacement?

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Go to Step 22

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22

Operate the system in order to verify the repair.

Did you correct the condition?

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System OK

Go to Step 2