GM Service Manual Online
For 1990-2009 cars only

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. Tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the VF dimming signal circuit is shorted to ground.

Step

Action

Value(s)

Yes

No

Schematic Reference: Head Up Display Schematics

1

Did you perform the Head Up Display Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - Head Up Display

2

  1. Turn the ignition ON, with the engine OFF.
  2. Adjust the HUD dimmer switch to full intensity.

Does the HUD image appear on the windshield?

--

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 3

3

  1. Install a scan tool.
  2. Turn the ignition ON, with the engine OFF.
  3. With a scan tool, observe the Ignition 3 parameter in the HUD Inputs data list.

Does the Ignition 3 parameter display On?

--

Go to Step 4

Go to Step 8

4

  1. Adjust the HUD dimmer switch to full intensity.
  2. With a scan tool, observe the VF Dim parameter in the HUD data list.

Does the scan tool indicate that the VF Dim parameter is near the specified value?

B+

Go to Step 13

Go to Step 5

5

  1. Turn the ignition OFF.
  2. Disconnect the HUD switch.
  3. Connect a test lamp between the ignition 3 voltage circuit of the HUD switch and a good ground.
  4. Turn the ignition ON, with the engine OFF.

Does the test lamp illuminate?

--

Go to Step 6

Go to Step 11

6

  1. Turn the ignition OFF.
  2. Connect a 3-amp fused jumper between the ignition 3 voltage circuit of the HUD switch and the VF dimming signal circuit.
  3. Turn the ignition ON, with the engine OFF.
  4. With a scan tool, observe the VF Dim parameter.

Does the scan tool indicate that the VF Dim parameter is near the specified value?

B+

Go to Step 9

Go to Step 7

7

Test the VF dimming signal circuit for an open, for high resistance, or for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 10

8

Test the ignition 3 voltage circuit of the HUD for an open, for high resistance, or for a short to ground. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 10

9

Inspect for poor connections at the harness connector of the HUD switch. 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 14

Go to Step 12

10

Inspect for poor connections at the harness connector of the HUD. 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 14

Go to Step 13

11

Repair the open, the high resistance, or the short to ground in the ignition 3 voltage circuit of the HUD switch. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 14

--

12

Replace the HUD switch. Refer to Head Up Display Switch Replacement .

Did you complete the replacement?

--

Go to Step 14

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13

Replace the HUD. Refer to Head Up Display Module Replacement .

Did you complete the replacement?

--

Go to Step 14

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14

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2