GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Was the entire Data Link Connector (DLC) system check performed?

--

Go to Step 2

Go to Data Link Communications System Check

2

Use a J 39200 , 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 3

Go to Step 4

3

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 5

Go to Step 6

4

Repair the poor connection or open in circuit 1550 between the DLC and ground.

Has the repair been made?

--

Go to Step 16

--

5

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 7

Go to Step 8

6

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

Is the repair complete?

--

Go to Step 16

--

7

  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 9

Go to Step 10

8

Determine if the scan tool is malfunctioning.

Refer to the scan tool instruction manual for additional information.

Is the action complete?

--

Go to Step 16

--

9

  1. Malfunction is not present or intermittent.
  2. Inspect the PCM, and pass key III module connectors for a poor connection, short to B+, or short to ground in CKT 1807. Repair as necessary.

Is the action complete?

--

Go to Step 16

--

10

  1. Turn the ignition switch to the OFF position.
  2. Disconnect the PCM connector C1.
  3. Use a J 39200 , 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 11

Go to Step 12

11

  1. Turn the ignition switch to RUN.
  2. Use a J 39200 , 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 13

Go to Step 14

12

Repair the short to ground in CKT 1807.

Is the repair complete?

--

Go to Step 16

--

13

Check continuity in circuit 1807 between the DLC terminal 2 and the PCM connector C1 terminal 59.

Is there continuity?

--

Go to Powertrain On Board Diagnostic (OBD) System Check in Engine Controls

Go to Step 15

14

  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 16

--

15

Repair the poor connection or an open in CKT 1807.

Is the repair complete?

--

Go to Step 16

--

16

  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

--