GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2000 🢒 Sunfire 🢒 Body and Accessories 🢒 Data Link Communications 🢒 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 number(s) below refer to the step number(s) 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. If communication can be established, the malfunction is in the instrument cluster, the radio, the SDM or the wiring between these devices

    8.

  8. If communication can be established, the malfunction is in the SDM, EBCM or the wiring between these devices.

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 leaving 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 8

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 Step 7

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 32

Go to Step 6

6

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

Go to DTC U1000 and DTC U1255 Class 2 Communication Malfunction

Go to DTC U1001-U1254 Loss of XXX Communications

7

Diagnose the malfunction using the DTC U1XXX Loss of XXX Communications procedures for the module which is not communicating. Refer to DTC U1001-U1254 Loss of XXX Communications

Did you complete the action?

Go to Control Module References for the applicable Diagnostic System Check

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8
  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 Control Module References for the applicable Diagnostic System Check

Go to Step 9

9

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 Control Module References for the applicable Diagnostic System Check

Go to Step 10

10

Test the class 2 serial data circuit of the DLC for an open between terminal 2 and connector C2 terminal B7 of the BCM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Control Module References for the applicable Diagnostic System Check

Go to Step 11

11
  1. Disconnect the PCM connector C1.
  2. Disconnect the radio connector C1 (base) or C2 (monsoon).
  3. Disconnect the instrument cluster connector.
  4. Install a scan tool.
  5. Turn ON the ignition leaving the engine OFF.
  6. 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 13

12
  1. Turn OFF the ignition.
  2. Disconnect the EBCM connector C1.
  3. Reconnect the PCM connector C1.
  4. Turn ON the ignition leaving the engine OFF.
  5. Attempt to communicate with the BCM or PCM through the class 2 serial data circuit.

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

Go to Step 14

Go to Step 15

13
  1. Turn OFF the ignition.
  2. Test the class 2 serial data circuit between the BCM and the following components for a short to ground or a short to voltage: (Turn ON the ignition leaving the engine OFF when you test for a short to voltage.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
    3. • DLC
    • PCM
    • IP cluster
    • Radio

Did you find and correct the condition?

Go to Control Module References for the applicable Diagnostic System Check

Go to Step 18

14
  1. Turn OFF the ignition.
  2. Disconnect the SDM connector.
  3. Reconnect the IP cluster connector.
  4. Turn ON the ignition leaving the engine OFF.
  5. Attempt to communicate with the BCM, PCM or IP cluster through the class 2 serial data circuit.

Does the scan tool communicate with the BCM, PCM or IP cluster on the Class 2 serial data circuit?

Go to Step 16

Go to Step 17

15
  1. Turn OFF the ignition.
  2. Test the class 2 serial data circuit between the PCM and the EBCM for a short to ground or a short to voltage. (Turn ON the ignition leaving the engine OFF when you test for a short to voltage.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Control Module References for the applicable Diagnostic System Check

Go to Step 19

16
  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, PCM, IP cluster or SDM through the class 2 serial data circuit.

Does the scan tool communicate with the BCM, PCM, IP cluster or SDM on the Class 2 serial data circuit?

Go to Step 23

Go to Step 21

17
  1. Turn OFF the ignition.
  2. Test the class 2 serial data circuit between the IP cluster and the SDM for a short to ground or a short to voltage. (Turn ON the ignition leaving the engine OFF when you test for a short to voltage.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Control Module References for the applicable Diagnostic System Check

Go to Step 20

18

Inspect for poor connections at the harness connector of the body control 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 Control Module References for the applicable Diagnostic System Check

Go to Step 26

19

Inspect for poor connections at the harness connector of the powertrain control 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 Control Module References for the applicable Diagnostic System Check

Go to Step 27

20

Inspect for poor connections at the harness connector of the IP cluster. 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 for the applicable Diagnostic System Check

Go to Step 28

21
  1. Turn OFF the ignition.
  2. Test the class 2 serial data circuit between the SDM and the EBCM for a short to ground or a short to voltage. (Turn ON the ignition leaving the engine OFF when you test for a short to voltage.) Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Control Module References for the applicable Diagnostic System Check

Go to Step 22

22

Inspect for poor connections at the harness connector of the SDM. 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 for the applicable Diagnostic System Check

Go to Step 29

23
  1. Turn OFF the ignition.
  2. Reconnect the EBCM connector.
  3. Turn ON the ignition leaving the engine OFF.
  4. Attempt to communicate with the BCM, PCM, IP cluster, EBCM or SDM through the class 2 serial data circuit.

Does the scan tool communicate with the BCM, PCM, IP cluster, EBCM or SDM on the Class 2 serial data circuit?

Go to Step 24

Go to Step 25

24

Inspect for poor connections at the harness connector of the radio. 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 for the applicable Diagnostic System Check

Go to Step 30

25

Inspect for poor connections at the harness connector of the EBCM. 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 for the applicable Diagnostic System Check

Go to Step 31

26

Replace the BCM. Refer to Body Control Module Replacement in Body Control System.

Did you complete the replacement?

Go to Step 32

--

27

Replace the PCM. Refer to Powertrain Control Module Replacement/Programming -2.2L or Powertrain Control Module Replacement/Programming -2.4L in Engine Controls.

Did you complete the replacement?

Go to Step 32

--

28

Replace the IP cluster. Refer to Instrument Cluster Replacement in Instrument Panel, Gauges and Console.

Did you complete the replacement?

Go to Step 32

--

29

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

Did you complete the replacement?

Go to Step 32

--

30

Replace the radio. Refer to Radio Replacement in Entertainment.

Did you complete the replacement?

Go to Step 32

--

31

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

Did you complete the replacement?

Go to Step 32

--

32
  1. Reconnect all of the disconnected modules.
  2. Connect any other disconnected connectors.
  3. Install a scan tool.
  4. Turn ON the ignition leaving 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. 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.)
  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 34

Go to Step 33

33

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

Go to Step 34

Go to Step 36

34

Diagnose the DTCs as directed by the diagnostic procedures for the particular module or malfunction. If the vehicle will start and run, the action is complete.

Did you complete the action?

Go to Step 35

--

35

Did you diagnose all of the DTCs?

Go to Step 36

Go to Step 34

36

Use the scan tool in order to clear the DTCs.

Did you complete the action?

System OK

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