GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Was the Data Link Communications System Check performed?

--

Go to Step 2

Go to Data Link Communications System Check

2

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

    • Engine Control Module (ECM)
    • Instrument Cluster
    • Memory Seat Module

Does the scan tool communicate with the other modules?

--

Go to Step 3

Go to Step 4

3

  1. Disconnect the transmission control module (TCM) connector.
  2. Measure the resistance between the TCM connector terminal 13 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 terminal 13. 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 CKT XM12 (BRN/WHT).

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 memory seat module.
  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 TCM.

Does the scan tool communicate with the TCM?

--

System OK

Go to Step 2

10

  1. Inspect the FLASHER fuse for an open.
  2. Inspect and test the TCM ignition feed circuit (CKT X837) at terminal 28 for proper voltage (11-13 V), with the key ON.
  3. Inspect and test the TCM ground circuits (CKTs F819 and F836) at terminals 19 and 35.
  4. Make necessary repairs.

Did you find and correct any conditions?

--

Go to Step 9

Go to Step 11

11

Replace the TCM.

Is the replacement complete?

--

Go to Step 9

--

12

Replace the memory seat module.

Is the replacement complete?

--

Go to Step 9

--

13

  1. Reconnect the memory seat module.
  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

Test the serial data circuit, of the DLC, for a short to ground between terminal 7 and each module.

    • 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 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.

    • 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 2

19

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

Is the repair complete?

--

Go to Step 9

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