GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Did you perform the Data Link Communications System Check?

--

Go to Step 2

Go to Diagnostic System Check - Data Link Communications

2

  1. Locate an identical vehicle with the same systems.
  2. Connect the scan tool to the second vehicles DLC.
  3. Establish communications with the second vehicle.

Can coomunications be established?

--

Go to Step 3

Go to scan tools owners manual.

3

  1. Disconnect the scan tool from the secondary vehicle.
  2. Ensure the ignition switch is in the OFF position on the original vehicle.
  3. Connect a testlamp between terminals 16 of the DLC and ground on the original vehicle.

Does the testlamp light?

--

Go to Step 4

Go to Step 6

4

Connect the testlamp between terminals 16 and 4, and then 16 and 5 of the DLC.

Does the testlamp light?

--

Go to Step 5

Go to Step 7

5

Inspect the power and ground circuits of the DLC for intermittents and poor connections. Refer to Intermittents and Poor Connections Diagnosis

Is the repair complete?

--

Go to Diagnostic System Check - Data Link Communications

--

6

Locate and repair the open in CKT 840 (ORN) between the AUX PWR fuse and the DLC. Refer to Wiring Repairs

Is the repair complete?

--

Go to Diagnostic System Check - Data Link Communications

--

7

Locate and repair the open in CKT 150 (BLK) or CKT 451 (BLK/WHT) between the DLC and ground. Refer to Wiring Repairs

Is the repair complete?

--

Go to Diagnostic System Check - Data Link Communications

--