U1301 Class II Data Link

DTC U1301 Class II Data Link (Part 1 Of 3):

DTC U1301 Class II Data Link (Part 2 Of 3):

DTC U1301 Class II Data Link (Part 3 Of 3):

CIRCUIT DESCRIPTION
The Body Control Module (BCM) transmits on the Class II serial data link. If the BCM receives normal messages from other modules a DTC code will set.

CONDITIONS FOR SETTING THE DTC
^ The BCM detects a short to voltage on the Class II serial data link.

ACTION TAKEN WHEN THE DTC SETS
^ Stores a DTC U1301 in the BCM memory.
^ No driver warning message will be displayed for this DTC.

CONDITIONS FOR CLEARING THE DTC
^ The BCM receives messages.
^ 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
^ DTC U1301 indicates that the Class II serial data link has been shorted to voltage. The BCM sends DTC information to the Tech 2 scan tool via the Class II serial data link. If the short to voltage is currently present, the Tech 2 scan tool will be unable to communicate with the BCM. Therefore, you will be unable to obtain a DTC U1301 as a current DTC. However, if the Tech 2 scan tool is able to communicate with the BCM and DTC U1301 is read, it will be a history DTC. Wiggle wires and connectors when performing circuit checks on the Class II serial data link. This can often cause the short to voltage to appear.
^ The following conditions may cause an intermittent malfunction to occur:
- An intermittent short to voltage in the Class II serial data link.
- Short to voltage internal to the BCM.
^ DTC P1626 will set in the Powertrain Control Module (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 U1301.
2. Checks for a short to B+ in circuit 1132 with the ignition switch in the OFF position.
4. Checks for a short to B+ in circuit 1037 when the ignition switch is OFF and then in RUN.
5. Determines if the short to B+ is in circuit 1037 or the BCM when the ignition switch is in RUN and then OFF.
6. Checks for a short to B+ in circuit 1038 when the ignition switch is OFF and then in RUN.
10. Determines if the short to B+ is in circuit 1038 or the Heater-AC Control when the ignition switch is in RUN and then OFF.
11. Checks for a short to B+ in circuit 1036 when the ignition switch is OFF and then in RUN.
14. Determines if the short to B+ is in circuit 1036 or the IPC when the ignition switch is in RUN and then OFF.
15. Checks for a short to B+ in circuit 1122 when the ignition switch is OFF and then in RUN.
18. Determines if the short to B+ is in circuit 1122 or the EBCM when the ignition switch is in RUN and then OFF.
19. Checks for a short to B+ in circuit 1049 when the ignition switch is OFF and then in RUN.
24. Determines if the short to B+ is in circuit 1049 or the PCM when the ignition switch is in RUN and then OFF.
25. Clears BCM DTCs and checks for BCM DTC U1301 again.
26. Checks for a short to B+ in circuit 1132 with the ignition in the RUN position.