GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2002 🢒 Montana 🢒 Restraints 🢒 SIR 🢒 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 trouble codes (DTCs) may be set due to this symptom and during this diagnostic procedure. Complete the diagnostic procedure in order to ensure all the DTCs are diagnosed and cleared from memory.

Diagnostic Aids
    • If a short to B+ is present, a history U1301 or U1305 will set in the modules. Refer to DTC U1300, U1301, or U1305 .
    • If a short to ground is present, a history U1300 or U1305 will set in the modules. Refer to DTC U1300, U1301, or U1305 .
    • Disconnecting modules and turning the ignition switch to RUN may cause DTCs in these modules. Check for DTCs in each module upon completion of the required repair.
    • The scan tool cannot directly communicate to the Rear Video/Audio/HVAC or Video Disc Player. Diagnosis is accomplished by checking communications with the Radio.

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. DTCs U1300, U1301, or U1305 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 having a current status. This indicates 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. A poor connection at the DLC terminal would cause this condition but will not set a DTC.

    6.

  6. An open in the class 2 serial data circuit between the DLC and the star connector will prevent the scan tool from communicating with any module. This condition will not set a DTC.

    7.

  7. The class 2 serial data circuit is shorted to voltage or ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When testing the wiring for a short, make sure there is not a module connected to the wire being tested. This test isolates the PCM class 2 serial data circuit.

    8.

  8. This test isolates the SDM class 2 serial data circuit.

    9.

  9. This test isolates the EBCM class 2 serial data circuit.

    10.

  10. This test isolates the IPC class 2 serial data circuit.

    11.

  11. This test isolates the PK3 class 2 serial data circuit.

    12.

  12. This test isolates the DIC class 2 serial data circuit.

    13.

  13. This test isolates the Radio class 2 serial data circuit.

    14.

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

    15.

  15. The communication malfunction may have prevented diagnosis of the customer complaint.

Step

Action

Yes

No

Schematic Reference: Data Link Connector Schematics

1

Does the scan tool power up?

Go to Step 2

Go to Scan Tool Does Not Power Up

2

  1. Turn ignition ON, engine OFF.
  2. Attempt to communicate with each 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 9

3

  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 do 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 Diagnostic Aids

4

Are history 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 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 33

Go to Step 6

6

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

Go to DTC U1000 and U1255

Go to DTC U1001-U1254

7

  1. Turn ignition OFF.
  2. Disconnect the scan tool from the data link connector (DLC).
  3. Inspect for poor connections/terminal tension at the DLC terminals 2 and 5. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Control Module References in Body Control System for the applicable Diagnostic System Check

Go to Step 8

8

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

Did you find and correct the condition?

Go to Control Module References in Body Control System for the applicable Diagnostic System Check

Go to Step 9

9

  1. Disconnect the star connector.
  2. Inspect for poor connections/terminal tension at the star connector. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Control Module References in Body Control System for the applicable Diagnostic System Check

Go to Step 10

10

Test the class 2 serial data circuit for an open, a short to ground or a short to B+ between the DLC terminal 2 and the star connector terminal A. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Control Module References in Body Control System for the applicable Diagnostic System Check

Go to Step 11

11

  1. Connect a jumper wire to the DLC terminal of the star connector.
  2. Connect the other end of the jumper wire to the PCM terminal of the star connector.
  3. Turn ignition ON, engine OFF.
  4. Attempt to communicate with the PCM.

Does the scan tool communicate with the PCM?

Go to Step 13

Go to Step 12

12
  1. Turn ignition OFF.
  2. Disconnect the PCM.
  3. Test the class 2 serial data circuit between the star connector and the PCM for a short to ground or a short to voltage. Turn on the ignition leaving the engine off when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 33

Go to Step 31

13

  1. Disconnect the jumper wire from the PCM terminal of the star connector.
  2. Connect the jumper wire to the SDM terminal of the star connector.
  3. Turn ignition ON, engine OFF.
  4. Attempt to communicate with the SDM.

Does the scan tool communicate with the SDM?

Go to Step 15

Go to Step 14

14
  1. Turn ignition OFF.
  2. Disconnect the SDM.
  3. Test the class 2 serial data circuit between the star connector and the SDM for a short to ground or a short to voltage. Turn ignition ON, engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 33

Go to Step 31

15

  1. Disconnect the jumper wire from the SDM terminal of the star connector.
  2. Connect the jumper wire to the EBCM terminal of the star connector.
  3. Turn ignition ON, engine OFF.
  4. Attempt to communicate with the EBCM.

Does the scan tool communicate with the EBCM?

Go to Step 17

Go to Step 16

16
  1. Turn ignition OFF.
  2. Disconnect the EBCM.
  3. Test the class 2 serial data circuit between the star connector and the EBCM for a short to ground or a short to voltage. Turn ignition ON, engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 33

Go to Step 31

17

  1. Disconnect the jumper wire from the EBCM terminal of the star connector.
  2. Connect the jumper wire to the IPC terminal of the star connector.
  3. Turn ignition ON, engine OFF.
  4. Attempt to communicate with the IPC.

Does the scan tool communicate with the IPC?

Go to Step 19

Go to Step 18

18
  1. Turn ignition OFF.
  2. Disconnect the IPC.
  3. Test the class 2 serial data circuit between the star connector and the IPC for a short to ground or a short to voltage. Turn ignition ON, engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 33

Go to Step 31

19

  1. Disconnect the jumper wire from the IPC terminal of the star connector.
  2. Connect the jumper wire to the theft deterrent control module terminal of the star connector.
  3. Turn ignition ON, engine OFF.
  4. Attempt to communicate with the theft deterrent control module.

Does the scan tool communicate with the theft deterrent control module?

Go to Step 21

Go to Step 20

20
  1. Turn ignition OFF.
  2. Disconnect the theft deterrent control module.
  3. Test the class 2 serial data circuit between the star connector and the theft deterrent control module for a short to ground or a short to voltage. Turn ignition ON, engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 33

Go to Step 31

21

  1. Disconnect the jumper wire from the theft deterrent control module terminal of the star connector.
  2. Connect the jumper wire to the DIC terminal of the star connector.
  3. Turn ignition ON, engine OFF.
  4. Attempt to communicate with the DIC.

Does the scan tool communicate with the DIC?

Go to Step 23

Go to Step 22

22
  1. Turn ignition OFF.
  2. Disconnect the DIC.
  3. Test the class 2 serial data circuit between the star connector and the DIC for a short to ground or a short to voltage. Turn ignition ON, engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 33

Go to Step 31

23

  1. Disconnect the jumper wire from the DIC terminal of the star connector.
  2. Connect the jumper wire to the Radio terminal of the star connector.
  3. Turn ignition ON, engine OFF.
  4. Attempt to communicate with the Radio.

Does the scan tool communicate with the Radio?

Go to Step 33

Go to Step 30

24
  1. Turn ignition OFF.
  2. Disconnect the class 2 serial data circuit from Rear Video/Audio/HVAC.
  3. Turn ignition ON, engine OFF.
  4. Attempt to communicate with the Radio.

Does the scan tool communicate with the Radio?

Go to Step 32

Go to Step 25

25
  1. Turn ignition OFF.
  2. Disconnect the Rear Video/Audio/HVAC class 2 serial data circuit at the Video Disc Player.
  3. Turn ignition ON, engine OFF.
  4. Attempt to communicate with the Radio.

Does the scan tool communicate with the Radio?

Go to Step 26

Go to Step 27

26
  1. Turn ignition OFF.
  2. Disconnect the Rear Video/Audio/HVAC and Video Disc Player.
  3. Test the class 2 serial data circuit between the Rear Video/Audio/HVAC and Video Disc Player for a short to ground or a short to voltage. Turn ignition ON, engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 33

Go to Step 31

27
  1. Turn ignition OFF.
  2. Disconnect the class 2 serial data circuit from Video Disc Player.
  3. Turn ignition ON, engine OFF.
  4. Attempt to communicate with the Radio.

Does the scan tool communicate with the Radio?

Go to Step 32

Go to Step 28

28
  1. Turn ignition OFF.
  2. Disconnect the Video Disc Player class 2 serial data circuit at the Radio.
  3. Turn ignition ON, engine OFF.
  4. Attempt to communicate with the Radio.

Does the scan tool communicate with the Radio?

Go to Step 29

Go to Step 30

29
  1. Turn ignition OFF.
  2. Disconnect the Video Disc Player and the Radio.
  3. Test the class 2 serial data circuit between the Video Disc Player and the Radio for a short to ground or a short to voltage. Turn ignition ON, engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 33

Go to Step 31

30
  1. Turn ignition OFF.
  2. Disconnect the Radio.
  3. Test the class 2 serial data circuit between the star connector and the Radio for a short to ground or a short to voltage. Turn ignition ON, engine OFF when testing for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 33

Go to Step 31

31

Inspect for poor connections/terminal tension at the class 2 serial data circuit of the module that is not communicating. 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 33

Go to Step 32

32

Important: Perform the setup procedure for the module if required.

Replace the module which is not communicating. Refer to Control Module References in Body Control System for the appropriate repair instructions for module replacement.

Did you complete the replacement?

Go to Step 33

--

33

  1. Reconnect all of the disconnected modules.
  2. Reconnect any other disconnected connectors.
  3. Install a scan tool.
  4. Turn ignition ON, engine OFF.
  5. Wait for 10 seconds. 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 prior to performing this test.
  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 you record any DTCs which begin with a "U" and with a current status?

Go to Step 35

Go to Step 34

34

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

Go to Step 35

Go to Step 37

35

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

Did you complete the action?

Go to Step 36

--

36

Did you diagnose all of the DTCs?

Go to Step 37

Go to Step 35

37

Clear the DTCs using the scan tool.

Did you complete the action?

System OK

--