U1300 Class II Data Link

DTC U1300 Class II Data Link (Part 1 Of 3):

DTC U1300 Class II Data Link (Part 2 Of 3):

DTC U1300 Class II Data Link (Part 3 Of 3):

CIRCUIT DESCRIPTION
The Body Control Module (BCM) transmits on die Class II serial data link. If the BCM sees a short to ground instead of its own transmitted message, a DTC code will set.

CONDITIONS FOR SETTING THE DTC
^ The BCM detects a short to ground in circuit 1132, the Class II serial data link.

ACTION TAKEN WHEN THE DTC SETS
^ Stores a DTC U1300 in the BCM memory.
^ No driver warning message will be displayed for this DTC.

CONDITIONS FOR CLEARING THE DTC
^ The DTC will clear when die fault is removed.
^ The BCM detects its own transmitted message.
^ 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 U1300 indicates that the Class II serial data link has been shorted to ground. The BCM sends DTC information to the Tech 2 scan tool via the Class II serial data link. If the short to ground is currently present, the Tech 2 scan tool will be unable to communicate with die BCM. Therefore, you will be unable to obtain a DTC U1300 as a current DTC. However, if the Tech 2 scan tool is able to communicate with the BCM and DTC U1300 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 ground to appear.
^ The following conditions may cause an intermittent malfunction to occur:
- An intermittent short to ground in the Class II serial data link. Refer to Data Link Connector for an electrical schematic. Diagrams
- Short to ground 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 Ul300.
2. Checks for a short to ground in circuit 1132.
4. Checks for a short to ground in circuit 1037.
5. Determines if the short to ground is in circuit 1037 or the BCM.
6. Checks for a short to ground in circuit 1038.
10. Determines if the short to ground is in circuit 1038 or the Heater-AC Control.
11. Checks for a short to ground in circuit 1036.
14. Determines if the short to ground is in circuit 1036 or the IPC.
15. Checks for a short to ground in circuit 1122.
18. Determines if the short to ground is in circuit 1122 or the EBCM.
19. Checks for a short to ground in circuit 1049.
24. Determines if the short to ground is in circuit 1049 or the PCM.
25. Clears BCM DTCs and checks for BCM DTC U1300 again.