GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Was the Data Link Communications Diagnostic System Check performed?

--

Go to Step 2

Go to A Diagnostic System Check - Data Link Communications

2

Attempt to establish communication with the other modules connected to the circuit.

    • Engine Control Module (ECM)
    • Memory Seat Module (MSM)
    • Transmission Control Module (TCM)

Does the scan tool communicate with the other modules?

--

Go to Step 3

Go to Step 20

3

  1. Disconnect the memory seat module (MSM) connector C1.
  2. Measure the resistance between the MSM connector C1 terminal 6 and the data link connector (DLC) terminal 7.

Does the resistance measure less than the specified value?

.5 ohms

Go to Step 5

Go to Step 6

4

  1. Disconnect the ECM connector.
  2. Attempt to communicate with the other modules.

Does the scan tool communicate with the other modules?

--

Go to Step 7

Go to Step 8

5

Inspect for poor connections at connector C1 terminal 6. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

Did you find and correct the poor connection condition?

--

Go to Step 9

Go to Step 10

6

Locate and repair an open in the MSM serial data circuit.

Is the repair complete?

--

Go to Step 9

--

7

Replace the ECM.

Is the replacement complete?

--

Go to Step 9

--

8

  1. Reconnect the ECM.
  2. Disconnect connector C1 from the MSM.
  3. Attempt to communicate with the other modules.

Does the scan tool communicate with the other modules?

--

Go to Step 12

Go to Step 13

9

Attempt to establish communications with the MSM.

Does the scan tool communicate with the MSM?

--

System OK

--

10

  1. Inspect the PWR SEAT fuse for an open.
  2. Inspect and test the MSM battery feed circuit at terminals 1 and 3 for proper voltage (11-13 V).
  3. Inspect and test the MSM ground circuits at terminals 2 and 5.
  4. Make necessary repairs.

Did you find and correct any conditions?

--

Go to Step 9

Go to Step 12

11

Replace the TCM.

Is the replacement complete?

--

Go to Step 9

--

12

Replace the MSM.

Is the replacement complete?

--

Go to Step 9

--

13

  1. Reconnect the MSM.
  2. Disconnect the TCM connector.
  3. Attempt to communicate with the other modules.

Does the scan tool communicate with the other modules?

--

Go to Step 11

Go to Step 14

14

  1. Reconnect the TCM.
  2. Disconnect the instrument cluster connector.
  3. Attempt to communicate with the other modules.

Does the scan tool communicate with the other modules?

--

Go to Step 15

Go to Step 16

15

Replace the instrument cluster.

Is the replacement complete?

--

Go to Step 9

--

16

  1. Disconnect each module on the serial data circuit (DLC terminal 7).
  2. Test the serial data circuit, of the DLC, for a short to ground. Refer to Testing for Short to Ground in Wiring Systems.
  3. Test between terminal 7 and the following terminals at each module:
  4. • ECM connector C2 terminal 53
    • Instrument Cluster connector terminal 24
    • Memory Seat Module connector C1 terminal 6
    • TCM connector terminal 51

Did you find a short to ground in the serial data circuit?

--

Go to Step 17

Go to Step 18

17

Locate and repair the short to ground in the serial data circuit.

Is the repair complete?

--

Go to Step 9

--

18

Test the serial data circuit, of the DLC, for a short to voltage between terminal 7 and each module. (Turn ON the ignition, leaving the engine OFF, when testing for a short to voltage.)

    • ECM connector terminal 88
    • Instrument Cluster connector terminal 24
    • Memory Seat Module connector C1 terminal 6
    • TCM connector terminal 13

Did you find a short to voltage in the serial data circuit?

--

Go to Step 19

Go to Step 21

19

Locate and repair the short to voltage in the serial data circuit.

Is the repair complete?

--

Go to Step 9

--

20

  1. Turn OFF the ignition.
  2. Disconnect the scan tool from the data link connector (DLC).
  3. Inspect for poor connections/terminal tension at the DLC terminal 7. Refer to Intermittents and Poor Connections Diagnosis in Wiring Systems.

Did you find and correct a poor connection condition?

--

Go to Step 2

Go to Step 4

21

Test the serial data circuit, of the DLC, for an open between terminal 7 and each module. Refer to Testing for Continuity in Wiring Systems.

    • ECM connector C2 terminal 53
    • Instrument Cluster connector terminal 24
    • Memory Seat Module connector C1 terminal 6
    • TCM connector terminal 51

Did you find an open in the serial data circuit?

--

Go to Step 9

--