GM Service Manual Online
For 1990-2009 cars only

Step

Action

Value(s)

Yes

No

1

Was the Data Link Connector (DLC) System Check performed?

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Go to Step 2

Go to Data Link Communications System Check

2

  1. Install a scan tool.
  2. Turn ON the scan tool.

Does the scan tool turn ON?

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System OK

Go to Step 3

3

  1. Disconnect the scan tool from the DLC.
  2. Connect a test lamp to ground.
  3. Probe the DLC connector terminal 16.

Did the test lamp light?

--

Go to Step 4

Go to Step 6

4

  1. Connect a test lamp to battery voltage.
  2. Probe the DLC connector terminal 4.

Did the test lamp light?

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Go to Step 5

Go to Step 7

5

  1. Connect a test lamp to battery voltage.
  2. Probe the DLC connector terminal 5.

Did the test lamp light?

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Go to Step 9

Go to Step 8

6

Locate and repair an open in CKT 1240.

Is the repair complete?

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Go to Step 11

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7

Locate and repair an open in CKT 150.

Is the repair complete?

--

Go to Step 11

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8

Locate and repair an open in CKT 851.

Is the repair complete?

--

Go to Step 11

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9

    • If the B+ and ground circuits are OK, the scan tool should power up.
    • Refer to the scan tool instruction manual.
    • Make sure the scan tool is capable of being powered by the DLC.

Have you verified that the scan tool is capable of being powered by the DLC?

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Go to Step 10

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10

Scan tool may be malfunctioning. Refer to scan tool instruction manual. Try using a different scan tool.

Is the replacement complete?

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Go to Step 11

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11

  1. Reconnect or install any connectors and components that were disconnected or removed.
  2. Verify that the scan tool operates properly.

Is the repair complete?

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System OK

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