GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2001 🢒 Montana Ext. 🢒 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 U1301 or DTC U1305 .
    • If a short to ground is present, a history U1300 or U1305 will set in the modules. Refer to DTC U1300 or DTC 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.

Test Description

  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 7

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 6

Go to Diagnostic Aids

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 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 27

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 or a short 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 27

Go to Step 25

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 27

Go to Step 25

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 27

Go to Step 25

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 27

Go to Step 25

19

  1. Disconnect the jumper wire from the IPC terminal of the star connector.
  2. Connect the jumper wire to the PK3 terminal of the star connector.
  3. Turn ignition ON, engine OFF.
  4. Attempt to communicate with the PK3 module.

Does the scan tool communicate with the PK3 module?

Go to Step 21

Go to Step 20

20
  1. Turn ignition OFF.
  2. Disconnect the PK3 module.
  3. Test the class 2 serial data circuit between the star connector and the PK3 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 27

Go to Step 25

21

  1. Disconnect the jumper wire from the PK3 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 22

Go to Step 23

22

  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 27

Go to Step 24

23

  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 27

Go to Step 25

24
  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 27

Go to Step 25

25

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 27

Go to Step 26

26

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 27

--

27
  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 29

Go to Step 28

28

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

Go to Step 29

Go to Step 31

29

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

Did you complete the action?

Go to Step 30

--

30

Did you diagnose all of the DTCs?

Go to Step 31

Go to Step 29

31

Clear the DTCs using the scan tool.

Did you complete the action?

System OK

--