GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Use a DMM in order to measure the voltage between B+ and DLC terminal 5.

Is the voltage within the specified range?

B+ (9-14 V)

Go to Step 2

Go to Step 3

2

Inspect for a proper connection of the scan tool to the DLC.

Is the connection OK between the scan tool and the DLC?

--

Go to Step 6

Go to Step 7

3

Does the instrument cluster display work?

--

Go to Step 4

Go to Step 5

4

Repair the poor connection or open in circuit 451 between the DLC and S215.

Has the repair been made?

--

Go to Step 17

--

5

Repair the poor connection or open in circuit 451 between S215 and G110.

Has the repair been made?

--

Go to Step 17

--

6

Use the scan tool in order to establish communication with the PCM on a different vehicle.

Can communication be established with the scan tool?

--

Go to Step 8

Go to Step 9

7

Repair the poor connection between the DLC and the scan tool.

Is the repair complete?

--

Go to Step 17

--

8

  1. Reconnect the scan tool to the DLC.
  2. Turn the ignition switch to RUN.
  3. Use a scan tool in order to establish communication with the Powertrain Control Module (PCM).

Can the scan tool communicate with the PCM?

--

Go to Step 10

Go to Step 11

9

Determine if the scan tool is malfunctioning.

Refer to the scan tool instruction manual for additional information.

Is the action complete?

--

Go to Step 17

--

10

  1. If malfunction is not present or intermittent, inspect the PCM connector for a poor connection, short to B+, or short to ground in CKT 1807.
  2. Repair as necessary.

Is the action complete?

--

Go to Step 17

--

11

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the PCM connector C1 (V6 VIN K) or C2 (V8 VIN G).
  3. Use a DMM in order to measure the resistance between the DLC terminal 2 and the DLC terminal 5.

Is the resistance the same as the specified value?

Infinite

Go to Step 12

Go to Step 13

12

  1. Turn the ignition switch to RUN.
  2. Use a DMM in order to measure the voltage between the DLC terminal 2 and the DLC connector terminal 5.

Is the voltage less than the specified value?

1 V

Go to Step 14

Go to Step 15

13

Repair the short to ground in CKT 1807.

Is the repair complete?

--

Go to Step 17

--

14

Check continuity in circuit 1807 between the DLC terminal 2 and the PCM connector C1 terminal 59 (V6 VIN K) or connector C2 terminal 58 (V8 VIN G).

Is there continuity?

--

Refer to PCM

Go to Step 16

15

  1. Turn the ignition switch to the OFF position.
  2. Repair the short to voltage in CKT 1807.

Is the repair complete?

--

Go to Step 17

--

16

Repair the poor connection or an open in CKT 1807.

Is the repair complete?

--

Go to Step 17

--

17

  1. Ensure that the ignition switch is in the OFF position.
  2. Reinstall connectors/components removed.

Is the action complete?

--

Go to Data Link Communications System Check

--