Data Link Communications

Diagnostic Trouble Code (DTC) Chart:

Wiring Schematic:

CIRCUIT DESCRIPTION
Class 2 control modules interface with each other through the class 2 serial data link.

CONDITIONS FOR SETTING THE DTC
A Class 2 control module detects a an open in the class 2 serial data link.

ACTIONS TAKEN WHEN THE DTC SETS
The class 2 control module that detects the open in the class 2 serial data link stores DTC U1000 in memory.

CONDITIONS FOR CLEARING THE DTC
^ The class 2 control module no longer detects an open in the class 2 serial data link.
^ Using a scan tool.

DIAGNOSTIC AIDS
^ DTC U1000 indicates that the class 2 serial data link is open to a particular control module. The class 2 control modules send DTC information to a scan tool via the class 2 serial data link. It the class 2 serial data link is currently open to one of the control modules, the scan tool will be unable to communicate with that particular control module. Therefore, you will be unable to obtain a DTC U1000 as a current DTC. However, if the scan tool is able to communicate with a class 2 control module and DTC U1000 is read, it will be a history DTC. Wiggle wires and connectors when performing circuit checks on the class 2 serial data link. This can often cause the open to reappear.
^ The following conditions may cause an intermittent malfunction to occur:
- An intermittent open in the class 2 serial data link.
- A class 2 control module is open internally.
^ 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 number(s) below refer to the step number(s) on the diagnostic table.
1. Checks for an open between the class 2 circuit and the module setting this DTC.
3. Determines whether the malfunction is intermittent or the module setting this DTC is faulty.