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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2004 🢒 GTO 🢒 Engine 🢒 Engine Electrical 🢒 Scan Tool Does Not Communicate with Class 2 Device

Circuit Description

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. Connecting a scan tool to the data link connector (DLC) allows communication with the modules for diagnostic purposes.

Diagnostic Aids

The engine will not start when there is a total loss of class 2 serial data communication while the ignition is OFF. The following conditions will cause a total loss of class 2 serial data communication:

    • A class 2 serial data circuit shorted to ground
    • A class 2 serial data circuit shorted to voltage
    • An internal condition within a module or connector on the class 2 serial data circuit, that causes a short to voltage or ground to the class 2 serial data circuit

Step

Action

Yes

No

Schematic Reference: Data Link Connector Schematics

Connector End View Reference: Data Link Communications Connector End Views

1

Does the scan tool power up?

Go to Step 2

Go to Scan Tool Does Not Power Up

2
  1. Turn ON the ignition, with the engine OFF.
  2. Attempt to communicate with the powertrain control module (PCM).

Does the scan tool communicate with the PCM on the class 2 serial data circuit?

System OK

Go to Step 3

3
  1. Turn OFF the ignition.
  2. Disconnect the scan tool from the data link connector (DLC).
  3. Inspect for poor connections and terminal tension at the DLC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Diagnostic Starting Point - Data Link Communications

Go to Step 4

4

Test the class 2 serial data circuits between the DLC and the PCM and between the PCM and the powertrain interface module (PIM) for the following conditions. Turn ON the ignition when testing for a short to voltage:

    • High resistance
    • Open
    • Short to ground
    • Short to voltage

Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 7

Go to Step 5

5

Inspect for poor connections and terminal tension at the harness connector of the suspect module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 7

Go to Step 6

6

Important: Perform the module programming or setup procedure if required.

Replace the suspect module.

Did you complete the replacement?

Go to Step 7

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7
  1. Connect all of the modules.
  2. Connect all the connectors.
  3. Install a scan tool.
  4. Turn ON the ignition leaving the engine OFF.

    5. Important: The scan tool may require a power up reset before communication will occur due to a short on the class 2 serial data circuit. Turn off or disconnect the scan tool before you display DTCs.

  5. Wait for 10 seconds.
  6. Select the display DTCs function for each module. If using a Tech 2, use the Class 2 DTC Check feature in order to determine which modules do have DTCs set.
  7. Record all of the displayed DTCs and the DTC status.

Did your record any DTCs which begin with a letter U and with a current status?

Go to Step 9

Go to Step 8

8

Did you record any DTCs which do not begin with a letter "U"?

Go to Step 9

Go to Step 10

9

Diagnose the DTCs as directed by the diagnostic procedures for the particular module or concern.

Did you complete the action?

Go to Step 10

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10

Did you diagnose all of the DTCs?

Go to Step 11

Go to Step 9

11

Clear the DTCs using the scan tool.

Did you complete the action?

Go to Diagnostic Starting Point - Data Link Communications

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