GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Were you sent here from the Data Link Communications Diagnostic System Check?

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Go to Step 2

Go to Diagnostic System Check - Data Link Communications

2

  1. Turn OFF the ignition switch.
  2. Install a scan tool.
  3. Disconnect the bus bars from star connector #1 and star connector #2.
  4. Connect Serial Data Link Tester J 42236-A to both star connectors.
  5. Important: Ensure the vehicle star connector #1 and star connector #2 correctly correspond with the serial data link tester connector #1 and connector #2. Refer to Data Link Connector Schematics .

  6. Place the switch located on the serial data link tester in the STAR CONNECTOR #1 position.
  7. Rotate the rotary switch to the (M) position.
  8. Turn ON the ignition switch.
  9. Use a scan tool in order to try to communicate with the BCM.

Can the scan tool communicate with the BCM?

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Go to Step 3

Go to Step 5

3

  1. Place the switch located on the serial data link tester to the STAR CONNECTOR #1 position.
  2. Using a scan tool, try to communicate with each of the following systems by rotating the rotary switch on the serial data link tester in the following positions (The Tech 2 Diagnostic Circuit Check/Class 2 Message Monitor may be used to display communication status with all systems):
  3. • (L) = HVAC (With CJ2)
    • (J) = RFA
    • (H) = RTD (if equipped)
    • (G) = IPC
    • (E) = TCS
    • (F) = SDM
    • (D) = RADIO
    • (B) = PCM

Can the scan tool communicate with all the systems?

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Go to Step 4

Go to Step 8

4

  1. Place the switch located on the serial data link tester to the STAR CONNECTOR #2 position.
  2. Using a scan tool, try to communicate with each of the following systems by rotating the rotary switch on the serial data link tester in the following positions (The Tech 2 Diagnostic Circuit Check/Class 2 Message Monitor may be used to display communication status with all systems):
  3. • (C) = LDCM
    • (D) = RDCM
    • (K) = SCM (if equipped)

Can the scan tool communicate with all the systems?

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Go to Step 10

Go to Step 8

5

  1. Turn OFF the ignition switch.
  2. Disconnect the serial data link tester J 42236-A.
  3. Both bus bars still disconnected from star connector #1 and star connector #2
  4. Using a DMM, check for continuity between DLC terminal 2 and star connector #1 terminal A.

Is there continuity?

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Go to Step 6

Go to Step 11

6

Using a DMM, check for continuity between DLC terminal 2 and ground.

Is there continuity?

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Go to Step 11

Go to Step 7

7

  1. Turn ON the ignition switch.
  2. Using a DMM, measure the voltage between DLC terminal 2 and ground.

Was any voltage measured?

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Go to Step 11

Go to Step 8

8

  1. Turn OFF the ignition switch.
  2. Disconnect the system module that did not communicate with the scan tool.
  3. Use a DMM to check for continuity between the applicable module terminal on star connectors and ground.

Is there continuity?

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Go to Step 12

Go to Step 9

9

  1. Turn ON the ignition switch.
  2. Connect a test light to ground.
  3. Probe the applicable star connector terminal to the system module that did not communicate.

Did the test lamp light?

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Go to Step 13

Go to Step 14

10

    • Check the serial data line for the following intermittent malfunctions:
    • Loose star connector #1 or #2
    • A short to ground
    • A short to voltage
    • An open circuit

Was an intermittent problem found and repaired?

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Go to Step 15

System OK

11

Locate and repair CKT 1132 for one of the following conditions:

    • A short to ground.
    • An open circuit.
    • A short to voltage.

Is repair complete?

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Go to Step 15

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12

Locate and repair a short to ground between applicable star connector terminal and the system module that did not communicate with the scan tool.

Is the repair complete?

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Go to Step 15

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13

Locate and repair a short to voltage between applicable star connector terminal and the system module that did not communicate with the scan tool.

Is the repair complete?

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Go to Step 15

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14

Replace the system module that did not communicate with the scan tool. Refer to the applicable module replacement procedure.

Is the replacement complete?

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Go to Step 15

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15

  1. Turn OFF the ignition switch.
  2. Reconnect or install any connector or components that were disconnected or removed.
  3. Clear all communication DTCs.
  4. Refer to the appropriate Diagnostic System Check for the module that did not communicate with the scan tool.

Is the repair complete?

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Go to Diagnostic System Check - Data Link Communications

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