GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1998 🢒 Regal 🢒 DTC 🢒 DTC U1040 Loss of Class 2 Communications with ABS

Object Number: 385137 Size: MF
Data Link Connector Schematics

Circuit Description

Class 2 control modules receive a state of health message from the Electronic Brake Traction Control Module (EBTCM) through the Class 2 serial data link.

Conditions for Setting the DTC

Class 2 control modules do not receive a state of health message from the EBTCM.

Action Taken When the DTC Sets
    • Class 2 control modules store DTC U1040 in memory.
    • The ABS indicator lamp turns on while the fault is present.

Conditions for Clearing the DTC
    • DTC U1040 will clear as a current DTC U1040 and will set as a history DTC U1040 when the class 2 control modules detect a state of health message from the EBTCM.
    • Using a scan tool.

Diagnostic Aids
    • The following conditions may cause an intermittent malfunction to occur:
      • An intermittent open or short to ground in circuit 1122.
      • Poor connections at the EBTCM.
      • An intermittent open in the Splice Pack SP205.
    • The Body Control Module (BCM) may store DTC U1040 if certain diagnostics are performed between the EBTCM and the Data Link Connector (DLC).
    • DTC P1626 will set in the Powertrain Control Module (PCM) when the ignition switch is on with the Body Control Module (BCM) disconnected. When BCM diagnostics and repairs are completed, refer to Engine Controls for additional information on PCM related DTCs.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests for an open in the Splice Pack SP205.

    2.

  2. This step tests for a short to ground in circuit 1122.

    3.

  3. This step tests for a short to B+ in circuit 1122.

    4.

  4. This step tests for an open in circuit 1122.

Step

Action

Value(s)

Yes

No

1

  1. Turn the ignition switch off.
  2. Disconnect the scan tool from the DLC.

    3. Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

  3. Disconnect battery negative terminal.
  4. Using a DMM, measure the resistance between the SP205 terminal A and each of the SP205 terminals B, E, G, L, and M; one terminal at a time.

Is the resistance measured less than the specified value?

2ohms

Go to Step 2

Go to Step 6

2

  1. Disconnect the Electronic Brake Traction Control Module (EBTCM) harness connector.
  2. Using a DMM, measure the resistance between the SP205 harness connector terminal E and ground.

Is the resistance measured same as the specified value?

∞

Go to Step 3

Go to Step 7

3

  1. Reconnect the battery negative terminal.
  2. Turn the ignition switch on.
  3. Using a DMM, measure the voltage between the SP205 harness connector terminal B and ground.

Is the voltage measured less than the specified value?

2 V

Go to Step 4

Go to Step 8

4

  1. Turn the ignition switch off.
  2. Using a DMM, measure the resistance between the SP205 harness connector terminal B and EBTCM harness connector terminal B7.

Is the resistance measured less than the specified value?

5ohms

Go to Step 5

Go to Step 9

5
  1. Reconnect the EBTCM connector.
  2. Turn the ignition switch on.
  3. Using a scan tool, communicate with the EBTCM.

Does the scan tool communicate with the EBTCM?

--

Go to Step 11

Go to Step 10

6

Replace the Splice Pack SP205.

Is the repair complete?

--

Go to Step 11

--

7

Repair short to ground in circuit 1122.

Is the repair complete?

--

Go to Step 11

--

8

Repair short to B+ in circuit 1122.

Is the repair complete?

--

Go to Step 11

--

9

Repair poor connection or open in circuit 1122.

Is the repair complete?

--

Go to Step 11

--

10
    • The integrity of the class 2 serial data link is OK. However, the Electronic Brake Traction Control Module (EBTCM) is not communicating class 2 data due to a fault within the EBTCM.
    • Refer to Diagnostic System Check in Antilock Brake System for further diagnosis.

Is the action complete?

--

Go to Step 11

--

11
  1. Turn the ignition switch off.
  2. Reinstall connectors/components removed and verify repairs.

Is the action complete?

--

System OK

--