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 the Data Link Connector DLC terminal 16 and the ground.

Is the voltage within the specified range?

B+ (9-14 V)

Go to Step 2

Go to Step 16

2

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 3

Go to Step 17

3

Use a DMM in order to measure the voltage between B+ and DLC terminal 4.

Is the voltage within the specified range?

B+ (9-14 V)

Go to Step 4

Go to Step 22

4

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 9

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 6

Go to Step 10

6

  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 11

Go to Step 7

7

  1. Turn the ignition switch to the LOCK position.
  2. Disconnect the PCM connector C1.
  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 8

Go to Step 12

8

  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 13

9

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

Is the repair complete?

--

Go to Step 15

--

10

Determine if the scan tool is malfunctioning.

Refer to the scan tool instruction manual for additional information.

Is the action complete?

--

Go to Step 15

--

11

If malfunction is not present or intermittent, inspect the PCM, SDM, and EBCM 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 15

--

12

Repair the short to ground in CKT 1807.

Is the repair complete?

--

Go to Step 15

--

13

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

Is the repair complete?

--

Go to Step 15

--

14

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

Is there continuity?

--

Refer to PCM

Go to Step 24

15

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

Is the action complete?

--

Go to Data Link Communications System Check

--

16

Does the radio work?

--

Go to Step 18

Go to Step 19

17

Does the instrument cluster display work?

--

Go to Step 22

Go to Step 23

18

Repair a poor connection or an open in circuit 640 between the DLC terminal 16 and S202.

Has the repair been made?

--

Go to Step 15

--

19

Check for fuse 10 for an open.

Is fuse 10 OK?

--

Go to Step 20

Go to Step 21

20

Repair a poor connection or an open in circuit 640 between the fuse block and S202.

Has the repair been made?

--

Go to Step 15

--

21

Replace fuse 10.

Has the repair been made?

--

Go to Step 15

--

22

Repair the poor connection or open in circuit 1550 between the DLC and S211.

Has the repair been made?

--

Go to Step 15

--

23

Repair the poor connection or open in circuit 1550 between S211 and G201.

Has the repair been made?

--

Go to Step 15

--

24

Repair the poor connection or an open in CKT 1807.

Is the repair complete?

--

Go to Step 15

--