GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you perform the Lighting Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

Are the backup lights ON with the ignition switch in the OFF position?

--

Go to Step 3

Go to Step 4

3

Disconnect the park/neutral switch.

are the backup lamps still ON?

--

Go to Step 4

Go to Step 5

4

Locate and repair short to voltage in CKT 24 (LT GRN).

Is the repair complete?

--

Go to Step 9

--

5

With the park/neutral switch disconnected, check for continuity with DMM between cavities C and F of connector C2.

Is continuity present?

--

Go to Step 6

Go to Step 4

6

With ignition OFF and park/neutral switch disconnected, check for B+ (battery voltage) from CKT 139 (PNK) to ground.

Is B+ present?

--

Go to Step 7

Go to Step 8

7

Locate and repair short to voltage in CKT 139 (PNK).

Is the repair complete?

--

Go to Step 8

--

8

Replace the park/neutral switch.

Refer to Park/Neutral Position Switch Replacement in Transmissions.

Is the repair complete?

--

Go to Step 9

--

9

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2