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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2005 🢒 Sunfire 🢒 Engine 🢒 Engine Electrical 🢒 Scan Tool Does Not Communicate with Class 2 Device

Circuit Description

Each module connected to the class 2 serial data circuit monitors serial data communication 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.

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • DTC U1300 Class 2 Data Link Low
    • DTC U1301 Class 2 Data Link High
    • DTC U1305 Class 2 Data Link Low or High

Diagnostic Aids
    • The engine will not start when there is a total malfunction of the class 2 serial data circuit while the engine is not running.
    • The power mode master (PMM) must be able to communicate with the other modules on the class 2 serial data bus in order for the Tech 2 to communicate with the other modules.
    • The powertrain control module (PCM) on this vehicle has 3 junctions to the class 2 serial data bus.

Test Description

The numbers below refer to the step numbers on the diagnostic table .

  1. A partial malfunction in the class 2 serial data circuit uses a different procedure from a total malfunction of the class 2 serial data circuit.

    2.

  2. The DTC U1300 and U1301 may be retrieved with a history status. These DTCs are not the cause of the present condition.

    3.

  3. A State of Health DTC with a history status may be present along with a DTC U1000 with a current status. This indicates that the malfunction occurred when the ignition was on.

    4.

  4. Data link connector terminals 2 and 5 provide the connection to the class 2 serial data circuit and the signal ground circuit respectively.

    5.

  5. An open in the class 2 serial data circuit between the DLC and the body control module (BCM) will prevent the scan tool from communicating with any module. This condition will not set a DTC.

    6.

  6. If communication can be established, the malfunction is not in the BCM or the wiring from the DLC to the BCM.

    7.

  7. This test attempts to establish communication with the radio.

    8.

  8. This test attempts to establish communication with the digital radio receiver (DRR).

    9.

  9. This test attempts to establish communication with the OnStar vehicle communications interface module (VCIM).

    10.

  10. This test attempts to establish communication with the PCM.

    11.

  11. This test attempts to establish communication with the instrument panel cluster (IPC).

    12.

  12. This test attempts to establish communication with the restraints sensing and diagnostic module (SDM).

    13.

  13. This test attempts to establish communication with the electronic brake control module (EBCM).

    14.

  14. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit of the BCM.

    15.

  15. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit of the radio.

    16.

  16. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit between the radio and the DRR module.

    17.

  17. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit between the radio and the VCIM module.

    18.

  18. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit of the PCM.

    19.

  19. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit of the IPC.

    20.

  20. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit of the SDM.

    21.

  21. This test analyzes the condition of the wiring and connectors in the class 2 serial data circuit of the EBCM.

    22.

  22. If there are no current DTCs that begin with a U, the communication malfunction has been repaired.

    23.

  23. The interruption of the class 2 serial data circuit may have prevented the diagnosis of the customer complaint.

Step

Action

Yes

No

Schematic Reference: Data Link Connector Schematics

Connector End View Reference: Master Electrical Component List and Inline Harness Connector End Views in Wiring Systems

1

Connect the scan tool to the data link connector.

Does the scan tool power up?

Go to Step 2

Go to Scan Tool Does Not Power Up

2

  1. Turn the ignition ON, with the engine OFF.
  2. Attempt to communicate with any module on the class 2 serial data circuit. If using a Tech 2, obtain this information using the class 2 Message Monitor feature.

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

Go to Step 3

Go to Step 7

3

  1. Select the Display DTCs function for each module. If using a Tech 2, use the class 2 Display DTCs feature in order to determine which modules have DTCs set.
  2. Record all of the displayed DTCs, the DTC status and the module which set the DTC.

Did you record any DTCs in the range of DTC U1000 to U1305?

Go to Step 4

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

4

Are the DTCs U1300, U1301 or U1305 retrieved from any module?

Go to Step 5

Go to Step 6

5

Important:: Turn the ignition ON, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions.

Test the class 2 serial data circuit for an intermittent short to ground or an intermittent short to voltage. Refer to the following in Wiring Systems:

    •  Circuit Testing
    •  Connector Repairs
    •  Wiring Repairs

Did you find and correct the condition?

Go to Step 35

Go to Step 6

6

Are DTCs U1000 or U1255 the only DTCs displayed in the previously specified range?

Go to DTC U1000 and U1255

Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information

7

  1. Turn the ignition OFF.
  2. Disconnect the scan tool from the data link connector (DLC).
  3. Inspect for poor connections at terminals 2 and 5 of 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 Step 35

Go to Step 8

8

Test the ground circuit at terminal 5 of the DLC for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 35

Go to Step 9

9

Inspect for poor connections at the body control module (BCM) connectors containing the class 2 serial data communication circuits. Refer to the following:

    •  Connector Repairs in Wiring Systems

Did you find and correct the condition?

Go to Step 35

Go to Step 10

10

Important:: Turn the ignition ON, with the engine OFF, when testing for a short to voltage. Use the DMM MIN/MAX function to capture intermittent conditions.

  1. Remove the connector from the BCM that contains the class 2 serial data circuit that originates from the DLC. Refer to Data Link Connector Schematics .
  2. Test the class 2 serial data circuit for a open circuit or high resistance between the DLC terminal 2 and the BCM connector that contains the class 2 serial data circuit that originates from the DLC. Refer to the following:
    3. •  Circuit Testing in Wiring Systems
    •  Wiring Repairs in Wiring Systems
  3. Test the class 2 serial data circuit for an short to B+ or ground between the DLC terminal 2 and the BCM connector that contains the class 2 serial data circuit that originates from the DLC. Refer to the following:
    4. •  Circuit Testing in Wiring Systems
    •  Wiring Repairs in Wiring Systems

Did you find and correct the condition?

Go to Step 35

Go to Step 11

11

  1. Reinstall the connector on the BCM that contains the class 2 serial data circuit that originates from the DLC. Refer to Data Link Connector Schematics .
  2. Disconnect the connector from the powertrain control module (PCM) that contains the class 2 serial data circuit that is run directly to the BCM and not through any other module. Refer to Data Link Connector Schematics .
  3. Disconnect the connector from the radio that contains the class 2 serial data circuit. Refer to Data Link Connector Schematics .
  4. If the vehicle is equipped with a digital radio receiver (DRR) module, disconnect the connector from the module that contains the class 2 serial data circuit. Refer to Data Link Connector Schematics .
  5. If the vehicle is equipped with a vehicle communication interface module (VCIM), disconnect the connector from the module that contains the class 2 serial data circuit. Refer to Data Link Connector Schematics .
  6. Disconnect the connector from the instrument panel cluster (IPC) that contains the class 2 serial data circuit. Refer to Data Link Connector Schematics .
  7. Install a scan tool.
  8. Turn the ignition ON, with the engine OFF.
  9. Attempt to communicate with the BCM through the class 2 serial data circuit.

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

Go to Step 12

Go to Step 19

12

  1. Turn the ignition OFF.
  2. Reinstall the connector that contains the class 2 serial data circuit on the radio.
  3. Turn the ignition ON, with the engine OFF.
  4. Attempt to communicate with the BCM and radio through the class 2 serial data circuit.

Does the scan tool communicate with the BCM and radio on the class 2 serial data circuit?

Go to Step 13

Go to Step 20

13

  1. If this vehicle is not equipped with a DRR module, answer yes and go to step 14.
  2. Turn the ignition OFF.
  3. Reinstall the connector that contains the class 2 serial data circuit on the DRR module.
  4. Turn the ignition ON, with the engine OFF.
  5. Attempt to communicate with the BCM and radio through the class 2 serial data circuit.

Does the scan tool communicate with the BCM, radio, and DRR on the class 2 serial data circuit?

Go to Step 14

Go to Step 21

14

  1. If this vehicle is not equipped with a VCIM, answer yes and go to step 15.
  2. Turn the ignition OFF.
  3. Reinstall the connector that contains the class 2 serial data circuit on the DRR module.
  4. Turn the ignition ON, with the engine OFF.
  5. Attempt to communicate with the BCM and radio through the class 2 serial data circuit.

Does the scan tool communicate with the BCM, radio, and VCIM on the class 2 serial data circuit?

Go to Step 15

Go to Step 22

15

  1. Turn the ignition OFF.
  2. Disconnect the connector from the electronic brake control module (EBCM) that contains the class 2 serial data circuit. Refer to Data Link Connector Schematics .
  3. Disconnect the connector from the sensing and diagnostic module (SDM) that contains the class 2 serial data circuit. Refer to Data Link Connector Schematics .
  4. Reconnect the PCM connector that contains the class 2 serial data circuit. Refer to Data Link Connector Schematics .
  5. Turn the ignition ON, with the engine OFF.
  6. Attempt to communicate with the BCM, radio, and PCM through the class 2 serial data circuit.

Does the scan tool communicate with the BCM, radio, and PCM on the class 2 serial data circuit?

Go to Step 16

Go to Step 23

16

  1. Turn the ignition OFF.
  2. Reconnect the IPC connector.
  3. Turn the ignition ON leaving the engine OFF.
  4. Attempt to communicate with the BCM, radio, PCM, and IPC through the class 2 serial data circuit.

Does the scan tool communicate with the BCM, radio, PCM, and IPC on the class 2 serial data circuit?

Go to Step 17

Go to Step 24

17

  1. Turn the ignition OFF.
  2. Reconnect the SDM connector.
  3. Turn the ignition ON leaving the engine OFF.
  4. Attempt to communicate with the BCM, radio, PCM, IPC, and SDM through the class 2 serial data circuit.

Does the scan tool communicate with the BCM, IPC, PCM, IPC, and SDM on the class 2 serial data circuit?

Go to Step 18

Go to Step 25

18

  1. Turn the ignition OFF.
  2. Reconnect the EBCM connector that contains the class 2 serial data circuit. Refer to Data Link Connector Schematics .
  3. Turn the ignition ON, with the engine OFF.
  4. Attempt to communicate with the BCM, radio, PCM, IPC, EBCM, and SDM through the class 2 serial data circuit.

Does the scan tool communicate with the BCM, radio, PCM, IPC, EBCM, and SDM on the class 2 serial data circuit?

Go to Step 35

Go to Step 26

19

  1. Turn the ignition OFF.
  2. Test the class 2 serial data circuit between the connector at the radio and the connector at the BCM for a short to B+ or ground. Refer to the following:
    3. •  Circuit Testing in Wiring Systems
    •  Wiring Repairs in Wiring Systems
  3. Test the exclusive class 2 serial data circuit between the connector at the PCM and the connector at the BCM for a short to B+ or ground. Refer to the following:
    4. •  Circuit Testing in Wiring Systems
    •  Wiring Repairs in Wiring Systems
  4. Test the exclusive class 2 serial data circuit between the connector at the IPC and the connector at the BCM for a short to B+ or ground. Refer to the following:
    5. •  Circuit Testing in Wiring Systems
    •  Wiring Repairs in Wiring Systems

Did you find and correct the condition?

Go to Step 35

Go to Step 27

20

  1. Turn the ignition OFF.
  2. Remove the connector that contains the class 2 serial data circuit from the radio. Refer to Data Link Connector Schematics .
  3. Remove the connector that contains the exclusive class 2 serial data circuit for the radio, from the BCM. Refer to Data Link Connector Schematics .
  4. Test the class 2 serial data circuit between the radio and BCM for a short to B+ or ground. Refer to the following:
    5. •  Circuit Testing in Wiring Systems
    •  Wiring Repairs in Wiring Systems
  5. Inspect for poor connections at the class 2 serial data circuit connector of the radio and of the BCM. Refer to the following:
    6. •  Connector Repairs in Wiring Systems

Did you find and correct the condition?

Go to Step 35

Go to Step 31

21

  1. Turn the ignition OFF.
  2. Remove the connector that contains the exclusive class 2 serial data circuit between the radio and the DRR module. Refer to Data Link Connector Schematics .
  3. Test the class 2 serial data circuit between the radio and the DRR module for a short to B+ or ground. Refer to the following:
    4. •  Circuit Testing in Wiring Systems
    •  Wiring Repairs in Wiring Systems
  4. Inspect for poor connections at the class 2 serial data circuit connector of the radio and of the DRR module. Refer to the following:
    5. •  Connector Repairs in Wiring Systems

Did you find and correct the condition?

Go to Step 35

Go to Step 32

22

  1. Turn the ignition OFF.
  2. Remove the connector that contains the exclusive class 2 serial data circuit between the radio and the VCIM. Refer to Data Link Connector Schematics .
  3. Test the class 2 serial data circuit between the radio and the VCIM for a short to B+ or ground. Refer to the following:
    4. •  Circuit Testing in Wiring Systems
    •  Wiring Repairs in Wiring Systems
  4. Inspect for poor connections at the class 2 serial data circuit connector of the radio and of the VCIM. Refer to the following:
    5. •  Connector Repairs in Wiring Systems

Did you find and correct the condition?

Go to Step 35

Go to Step 33

23

  1. Turn the ignition OFF.
  2. Remove the connector that contains the class 2 serial data circuit from the PCM. Refer to Data Link Connector Schematics .
  3. Test the exclusive class 2 serial data circuit between the PCM and the BCM for a short to B+ or ground. Refer to the following:
    4. •  Circuit Testing in Wiring Systems
    •  Wiring Repairs in Wiring Systems
  4. Test the exclusive class 2 serial data circuit between the PCM and the EBCM for a short to B+ or ground. Refer to the following:
    5. •  Circuit Testing in Wiring Systems
    •  Wiring Repairs in Wiring Systems
  5. Test the exclusive class 2 serial data circuit between the PCM and the SDM for a short to B+ or ground. Refer to the following:
    6. •  Circuit Testing in Wiring Systems
    •  Wiring Repairs in Wiring Systems
  6. Inspect for poor connections at the connector on the PCM that contains the class 2 serial data circuit. Refer to the following:
    7. •  Connector Repairs in Wiring Systems

Did you find and correct the condition?

Go to Step 35

Go to Step 28

24

  1. Turn the ignition OFF.
  2. Disconnect the connector that contains the exclusive class 2 serial data circuit between the IPC and the BCM, from the BCM. Refer to Data Link Connector Schematics .
  3. Disconnect the IPC connector.
  4. Test the exclusive class  2 serial data circuit between the IPC connector and the BCM for a short to B+ or ground. Refer to the following:
    5. •  Circuit Testing in Wiring Systems
    •  Wiring Repairs in Wiring Systems
  5. Test the exclusive class 2 serial data circuit between the IPC connector and the SDM connector for a short to B+ or ground. Refer to the following:
    6. •  Circuit Testing in Wiring Systems
    •  Wiring Repairs in Wiring Systems
  6. Inspect for poor connections at the harness connector of the IPC. Refer to the following:
    7. •  Connector Repairs in Wiring Systems

Did you find and correct the condition?

Go to Step 35

Go to Step 29

25

  1. Turn the ignition OFF.
  2. Disconnect the IPC connector.
  3. Disconnect the SDM connector.
  4. Test the exclusive class 2 serial data circuit between the IPC connector and the SDM connector for a short to B+ or ground. Refer to the following:
    5. •  Circuit Testing in Wiring Systems
    •  Wiring Repairs in Wiring Systems
  5. Test the exclusive class 2 serial data circuit between the EBCM and the SDM connector for a short to B+ or ground. Refer to the following:
    6. •  Circuit Testing in Wiring Systems
    •  Wiring Repairs in Wiring Systems
  6. Inspect for poor connections at the harness connector of the SDM and IPC. 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 35

Go to Step 30

26

  1. Turn the ignition OFF.
  2. Disconnect the SDM connector.
  3. Disconnect the connector that contains the class 2 serial data circuit from the PCM . Refer to Data Link Connector Schematics .
  4. Disconnect the connector that contains the class 2 serial data circuit from EBCM. Refer to Data Link Connector Schematics .
  5. Inspect for poor connections at the harness connector of the SDM, EBCM, and PCM. 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 35

Go to Step 34

27

Replace the BCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 35

--

28

Replace the PCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 35

--

29

Replace the IPC. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 35

--

30

Replace the SDM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 35

--

31

Important: Setup and reprogram the radio.

Replace the radio. Refer to Radio Replacement in Entertainment.

Did you complete the replacement?

Go to Step 35

--

32

Replace the DRR module. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 35

--

33

Replace the VCIM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 35

--

34

Replace the EBCM. Refer to Control Module References for replacement, setup, and programming.

Did you complete the replacement?

Go to Step 35

--

35

  1. Reconnect all of the disconnected modules.
  2. Connect any other disconnected connectors.
  3. Install a scan tool.
  4. Turn the ignition ON, with the ignition 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. Attempt to communicate with each module on the class 2 serial data circuit.

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

Go to Step 36

Go to Step 2

36

  1. 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 have DTCs set.
  2. Record all of the displayed DTCs and the DTC status.

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

Go to Step 38

Go to Step 37

37

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

Go to Step 38

Go to Step 40

38

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

Did you complete the action?

Go to Step 39

--

39

Did you diagnose all of the DTCs?

Go to Step 40

Go to Step 38

40

Clear the DTCs with the scan tool.

Did you complete the action?

System OK

--