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For 1990-2009 cars only
Makes 🢒 Buick 🢒 2000 🢒 LeSabre 🢒 Body and Accessories 🢒 Keyless Entry 🢒 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, U1301, and 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 or a U1255 with a current status. This indicates that the malfunction occurred when the ignition was on.

    4.

  4. The head up display (HUD), the memory seat module (MSM), and the remote function actuator (RFA) are not monitored by other modules. When one of these modules is not communicating, diagnose the malfunction using the specified procedure.

    5.

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

    6.

  6. An open in the class 2 serial data circuit between the DLC and connector C201 (w/o UV6) or splice S202 (w/UV6) 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 to ground. The condition may be due to the wiring or due to a malfunction in one of the modules. When you test the wiring for a short, make sure there is not a module connected to the wire being tested.

    8.

  8. If communication can be established, the malfunction is in the rear integration module (RIM); the compact disc changer (CDX), if equipped with U1S; the sensing and diagnostic module (SDM); or the wiring between these devices

    9.

  9. If communication can be established, the malfunction is in the remote function actuator (RFA), or the wiring between the RFA and the RIM.

    10.

  10. If communication can be established, the malfunction is in the electronic brake control module (EBCM); the memory seat module (MSM), if equipped with A45; or the wiring between these devices and the RFA. If communication cannot be established, the malfunction is in the powertrain control module (PCM), or the wiring between the PCM and the EBCM.

    11.

  11. If communication can be established, the malfunction is in the driver door module (DDM), the vehicle theft deterrent (VTD), or the wiring between the PCM and the flex wiring harness.

    12.

  12. If communication cannot be established, the malfunction is in the wiring between the VTD and connector C215.

    13.

  13. If communication can be established, the malfunction is in the climate control panel (CCP), if equipped with C67; the integrated radio chassis (IRC); the instrument panel cluster (IPC); or the flex wiring harness. When the malfunction is in the flex wiring harness, the flex wiring harness must be replaced. If communication cannot be established, the malfunction is in the dash integration module (DIM); the head up display (HUD), if equipped with UV6; the instrument panel integration module (IPM), if equipped with CJ2; or the wiring connected to the DLC at terminal 2.

    14.

  14. Since the short is not in the wiring harness the malfunction is due to one of the modules.

    15.

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

    16.

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

Step

Action

Yes

No

1

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 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 10

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 Step 9

6

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

Go to Step 7

Go to Step 8

7

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 8

8

Are U1000 or U1255 the only DTCs 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

9

Diagnose the malfunction using the DTC U1001 -- U1254 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 the Control Module References in Body Control Systems for the applicable Diagnostic System Check

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10
  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 and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

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

Go to Step 11

11

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 the Control Module References in Body Control Systems for the applicable Diagnostic System Check

Go to Step 12

12

Test the class 2 serial data circuit of the DLC for an open between terminal 2 and connector C201 (w/o UV6) or splice S202 (w/UV6). Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

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

Go to Step 13

13
  1. Disconnect the PCM connector C1.
  2. Disconnect the SDM.
  3. Install a scan tool.
  4. Turn ON the ignition leaving the engine OFF.
  5. Attempt to communicate with any module still connected to the DLC through the class 2 serial data circuit.

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

Go to Step 14

Go to Step 21

14
  1. Turn OFF the ignition.
  2. Reconnect the PCM connector C1.
  3. Disconnect the RIM.
  4. Turn ON the ignition leaving the engine OFF.
  5. Attempt to communicate with any module still connected to the DLC through the class 2 serial data circuit.

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

Go to Step 15

Go to Step 16

15
  1. Turn OFF the ignition.
  2. Test the class 2 serial data circuit between the RIM 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 Step 32

Go to Step 28

16
  1. Turn OFF the ignition.
  2. Disconnect the RFA.
  3. Turn ON the ignition leaving the engine OFF.
  4. Attempt to communicate with any module still connected to the DLC through the class 2 serial data circuit.

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

Go to Step 17

Go to Step 18

17
  1. Turn OFF the ignition.
  2. Test the class 2 serial data circuit between the RFA and the RIM 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 Step 32

Go to Step 28

18
  1. Turn OFF the ignition.
  2. Disconnect the EBCM.
  3. Turn ON the ignition leaving the engine OFF.
  4. Attempt to communicate with any module still connected to the DLC through the class 2 serial data circuit.

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

Go to Step 19

Go to Step 20

19
  1. Turn OFF the ignition.
  2. Test the class 2 serial data circuit between the EBCM and the RFA 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 Step 32

Go to Step 28

20
  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 Step 32

Go to Step 28

21
  1. Turn OFF the ignition.
  2. Disconnect connector C215.
  3. Turn ON the ignition leaving the engine OFF.
  4. Attempt to communicate with any module still connected to the DLC through the class 2 serial data circuit.

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

Go to Step 22

Go to Step 24

22
  1. Turn OFF the ignition.
  2. Connect connector C215.
  3. Disconnect the VTD.
  4. Turn ON the ignition leaving the engine OFF.
  5. Attempt to communicate with any module still connected to the DLC through the class 2 serial data circuit.

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

Go to Step 23

Go to Step 30

23

Test the class 2 serial data circuit between the VTD and the PCM 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 Step 32

Go to Step 28

24
  1. Turn OFF the ignition.
  2. Disconnect connector C216.
  3. Turn ON the ignition leaving the engine OFF.
  4. Attempt to communicate with any module still connected to the DLC through the class 2 serial data circuit.

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

Go to Step 25

Go to Step 26

25
  1. Turn OFF the ignition.
  2. Test the class 2 serial data circuit in the flex wiring harness 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 Step 32

Go to Step 28

26
  1. Turn OFF the ignition.
  2. Disconnect the DIM.
  3. Test the class 2 serial data circuit between the DIM 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.)

Did you find and correct the condition?

Go to Step 32

Go to Step 27

27

Test the class 2 serial data circuit of the DLC 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 Step 32

Go to Step 28

28

    Important: The DIM must be connected to the class 2 serial data circuit when attempting to communicate. The DIM informs other modules on the class 2 serial data circuit of the ignition switch position.

  1. Connect all of the disconnected modules except for those in the suspect area of the class 2 serial data circuit.
  2. Connect any other disconnected connectors.
  3. Connect one of the disconnected modules in the suspect area of the class 2 serial data circuit.
  4. Install a scan tool.
  5. Turn ON the ignition leaving the engine OFF.
  6. Attempt to communicate with any module still connected to the DLC through the class 2 serial data circuit.

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

Go to Step 29

Go to Step 30

29

Continue connecting the disconnected modules and attempting to communicate after each connection until communication cannot be established or all the modules are connected.

Did you find the condition?

Go to Step 31

Go to Step 32

30

Repair the class 2 serial data circuit between the VTD and C215. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 32

--

31

Replace the most recently connected module. Refer to Control Module References in Body Control Systems for the appropriate Repair Instructions for module replacement.

Did you complete the replacement?

Go to Step 32

--

32
  1. Connect all of the disconnected modules.
  2. Connect any other disconnected connectors.
  3. Install a scan tool.
  4. Turn ON the ignition leaving the engine 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 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 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. The PCM may have DTC(s) P1602 to P1615, or P1626 set. If only P1600 DTC(s) in the range specified along with history U1xxx DTC(s) are set and 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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