U1040 EBCM Class II Source ID 28

DTC U1040 EBCM Class II Source ID 28 (Part 1 Of 2):

DTC U1040 EBCM Class II Source ID 28 (Part 2 Of 2):

CIRCUIT DESCRIPTION
The Body Control Module (BCM) receives a state of health message from the module whose source ID it has learned. If the BCM does not see a state of health message from the Electronic Brake Control Module (EBCM), a DTC code will set.

CONDITIONS FOR SETTING THE DTC
^ The BCM does not receive a state of health from the EBCM.

ACTION TAKEN WHEN THE DTC SETS
^ Stores a DTC U1040 in the BCM memory.
^ No driver warning message will be displayed for this DTC.

CONDITIONS FOR CLEARING THE DTC
^ Under all fault conditions, the ignition switch must be cycled from the OFF position to the RUN position before this DTC can change from current to history.
^ DTC U1040 will clear as a current DTC U1040 and will set as a history DTC U1040 when the BCM detects a state of health message from the PCM.
^ A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.
^ 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 or 1037.
- Poor connections at the BCM, or the PCM.
- An intermittent in Splice Pack SP205.
^ The BCM may store DTC U1040 if certain diagnostics are performed between the EBCM and the Data Link Connector (DLC).
^ DTC P1626 will set in the PCM when the ignition switch is in the RUN position with the BCM disconnected.

TEST DESCRIPTION
Numbers below refer to the step numbers on the diagnostic table.
1. Always perform the BCM Diagnostic System Check before attempting to diagnose a DTC U1040.
3. Clears BCM DTCs and checks for BCM DTC U1040 again.
4. Checks if the scan tool tries to communicate with the EBCM.
5. Checks for a poor connection at the EBCM.
6. Checks if the Splice Pack SP205 is seated properly.
7. Checks for a poor connection at the BCM.
9. Checks the serial data link for an open between the EBCM and the BCM.
10. Connects the Splice Pack SP205 properly and tries to communicate with the EBCM again.
11. Checks for a poor connection at the Splice Pack.
14. Checks for an open in circuit 1122.