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For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2002 🢒 Sunfire 🢒 HVAC 🢒 Heating, Ventilation and Air Conditioning 🢒 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 DLC allows communication with the modules for diagnostic purposes.

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.

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 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 PCM.

    9.

  9. This test attempts to establish communication with the IPC.

    10.

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

    11.

  11. This test attempts to establish communication with the EBCM.

    12.

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

    13.

  13. This test analyzes the condition of the wiring and connectors in the Class 2 serial data circuit of the Radio.

    14.

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

    15.

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

    16.

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

    17.

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

    18.

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

    19.

  19. The interruption of the Class 2 serial data circuit may have prevented the diagnosis of the customer complaint.

Step

Action

Yes

No

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 ON the ignition 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 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 ON the ignition, 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 29

Go to Step 6

6

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

Go to DTC U1000 and U1255

Go to Diagnostic Trouble Code (DTC) List

7

  1. Turn OFF the ignition.
  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 29

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 29

Go to Step 9

9

Inspect for poor connections at the BCM connectors containing the Class  2 serial data communication circuits. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Refer to Data Link Connector Schematics for circuit and connector IDs.

Did you find and correct the condition?

Go to Step 29

Go to Step 10

10

Important:: Turn ON the ignition, 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 Data Link Connector. Refer to Data Link Connector Schematics for circuit and connector IDs.
  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 Circuit Testing and Wiring Repairs in Wiring Systems. Refer to Data Link Connector Schematics for circuit and connector IDs.
  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 Circuit Testing and Wiring Repairs in Wiring Systems. Refer to Data Link Connector Schematics for circuit and connector IDs.

Did you find and correct the condition?

Go to Step 29

Go to Step 11

11

  1. Reinstall the connector on the BCM that contains the Class  2 serial data circuit that originates from the Data Link Connector. Refer to Data Link Connector Schematics for circuit and connector IDs.
  2. Disconnect the connector from the 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 for circuit and connector IDs.
  3. Disconnect the connector from the Radio that contains the Class  2 serial data circuit. Refer to Data Link Connector Schematics for circuit and connector IDs.
  4. Disconnect the connector from the IPC that contains the Class  2 serial data circuit. Refer to Data Link Connector Schematics for circuit and connector IDs.
  5. Install a scan tool.
  6. Turn ON the ignition with the engine OFF.
  7. 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 17

12

  1. Turn Off the ignition.
  2. Reinstall the connector that contains the Class  2 serial data circuit on the Radio.
  3. Turn on the ignition 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 18

13

  1. Turn OFF the ignition.
  2. Disconnect the connector from EBCM that contains the Class  2 serial data circuit. Refer to Data Link Connector Schematics for circuit and connector IDs.
  3. Reconnect the PCM connector that contains the Class  2 serial data circuit. Refer to Data Link Connector Schematics for circuit and connector IDs.
  4. Turn ON the ignition with the engine OFF.
  5. 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 14

Go to Step 19

14

  1. Turn OFF the ignition.
  2. Disconnect the SDM connector.
  3. Reconnect the IPC connector.
  4. Turn ON the ignition leaving the engine OFF.
  5. 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 15

Go to Step 20

15

  1. Turn OFF the ignition.
  2. Reconnect the SDM connector.
  3. Turn ON the ignition 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 16

Go to Step 21

16

  1. Turn OFF the ignition.
  2. Reconnect the EBCM connector that contains the Class  2 serial data circuit. Refer to Data Link Connector Schematics in Body Control System for circuit and connector IDs.
  3. Turn ON the ignition 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 29

Go to Step 22

17

  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 Circuit Testing and Wiring Repairs in Wiring Systems. Refer to Data Link Connector Schematics for circuit and connector IDs.
  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 Circuit Testing and Wiring Repairs in Wiring Systems. Refer to Data Link Connector Schematics for circuit and connector IDs.
  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 Circuit Testing and Wiring Repairs in Wiring Systems. Refer to Data Link Connector Schematics for circuit and connector IDs.

Did you find and correct the condition?

Go to Step 29

Go to Step 23

18

  1. Turn OFF the ignition.
  2. Remove the connector that contains the Class  2 serial data circuit from the Radio. Refer to Data Link Connector Schematics for circuit and connector IDs.
  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 for circuit and connector IDs.
  4. Test the Class  2 serial data circuit between the Radio and BCM for a short to B+ or ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Refer to Data Link Connector Schematics for circuit and connector IDs.
  5. Inspect for poor connections at the Class  2 serial data circuit connector of the Radio and of the BCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Refer to Data Link Connector Schematics for circuit and connector IDs.

Did you find and correct the condition?

Go to Step 29

Go to Step 27

19

  1. Turn OFF the ignition.
  2. Remove the connector that contains the Class  2 serial data circuit from the PCM. Refer to Data Link Connector Schematics for circuit and connector IDs.
  3. Test the exclusive Class  2 serial data circuit between the PCM and the BCM for a short to B+ or ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Refer to Data Link Connector Schematics for circuit and connector IDs.
  4. Test the exclusive Class  2 serial data circuit between the PCM and the EBCM for a short to B+ or ground. Refer to Circuit Testing and Wiring Repairs in wiring systems. Refer to Data Link Connector Schematics for circuit and connector IDs.
  5. Inspect for poor connections at the connector on the PCM that contains the Class  2 serial data circuit. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Refer to Data Link Connector Schematics in Data Link Communications for circuit and connector IDs.

Did you find and correct the condition?

Go to Step 29

Go to Step 24

20

  1. Turn OFF the ignition.
  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 for circuit and connector IDs.
  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 Circuit Testing and Wiring Repairs in Wiring Systems. Refer to Data Link Connector Schematics for circuit and connector IDs.
  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 Circuit Testing and Wiring Repairs in wiring systems. Refer to Data Link Connector Schematics for circuit and connector IDs.
  6. Inspect for poor connections at the harness connector of the IPC. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Refer to Data Link Connector Schematics for circuit and connector IDs.

Did you find and correct the condition?

Go to Step 29

Go to Step 25

21

  1. Turn Off the ignition.
  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 Circuit Testing and Wiring Repairs in Wiring Systems. Refer to Data Link Connector Schematics for circuit and connector IDs.
  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 Circuit Testing and Wiring Repairs in wiring systems. Refer to Data Link Connector Schematics for circuit and connector IDs.
  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 29

Go to Step 26

22

  1. Turn Off the ignition.
  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 for circuit and connector IDs.
  4. Disconnect the connector that contains the Class  2 serial data circuit from EBCM. Refer to Data Link Connector Schematics for circuit and connector IDs.
  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 29

Go to Step 28

23

Important: Setup and Reprogram the BCM

Replace the BCM. Refer to Body Control Module Replacement for circuit and connector IDs.

Did you complete the replacement?

Go to Step 29

--

24

Important: Setup and Reprogram the PCM

Replace the PCM. Refer to Powertrain Control Module Replacement -LN2 or Powertrain Control Module Replacement -L61 or Powertrain Control Module Replacement -2.4L in Engine Controls.

Did you complete the replacement?

Go to Step 29

--

25

Important: Setup and Reprogram the IPC

Replace the IPC. Refer to Instrument Cluster Replacement in Instrument Panel, Gages, and Console.

Did you complete the replacement?

Go to Step 29

--

26

Important: Setup and Reprogram the SDM

Replace the SDM. Refer to Inflatable Restraint Sensing and Diagnostic Module Replacement in SIR.

Did you complete the replacement?

Go to Step 29

--

27

Important: Setup and Reprogram the Radio

Replace the Radio. Refer to Radio Replacement in Entertainment.

Did you complete the replacement?

Go to Step 29

--

28

Important: Setup and Reprogram the EBCM

Replace the EBCM. Refer to Electronic Brake Control Module Replacement in Antilock Brake System.

Did you complete the replacement?

Go to Step 29

--

29

  1. Reconnect all of the disconnected modules.
  2. Connect any other disconnected connectors.
  3. Install a scan tool.
  4. Turn ON the ignition 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 30

Go to Step 2

30
  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 32

Go to Step 31

31

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

Go to Step 32

Go to Step 34

32

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

Did you complete the action?

Go to Step 33

--

33

Did you diagnose all of the DTCs?

Go to Step 34

Go to Step 32

34

Use the scan tool in order to clear the DTCs.

Did you complete the action?

System OK

--