U2103

DTC U2103

Circuit Description

Modules connected to the GMLAN serial data circuits monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. The modules have programmed information about what messages are needed to be exchanged on the serial data circuits, for each virtual network. The messages are also supervised and some periodic messages are used by the receiver module as an availability indication of the transmitter module.

DTC U2103 will set when fewer modules are detected on the buss before the modules can learn the other module's IDs. If the communication buss is opened, or if the a modules power supply is lost when the vehicle is in the OFF power mode, and then placed in the RUN power mode, U2103 will set in specific modules.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC U2103 Fewer Controllers On Than Programmed.

When more than one U2103 DTC is set in either one module or in several modules, diagnose the DTCs in the following order:

1. Current DTCs before history DTCs unless told otherwise in the diagnostic table.
2. The DTC which is reported the most times.

This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description.





Conditions for Running the DTCs

* Voltage supplied to the modules is in the normal operating voltage range.
* The vehicle power mode requires serial data communication to occur.
* The DTC U2100 does not have a current status.

Conditions for Setting the DTC

A supervised periodic message that includes the transmitter module availability has not been received.

Action Taken When the DTC Sets

The module uses a default value for the missing parameter.

Conditions for Clearing the DTC

* A current DTC clears when the malfunction is no longer present.
* A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Diagnostic Aids

* A poor connection at the inoperative module may cause this code to set.
* An improperly powered module may cause this code to set.

Test Description

Step 1 - Step 9:

Step 10 - Step 12:

The numbers below refer to the step numbers on the diagnostic table:
3. GIf body control module (BCM) will not power up the vehicle cannot establish the correct power mode. This step tests for the correct power supply conditions for the BCM.
4. If DTC U2103 is set as history and you can communicate with the suspect module, the malfunction is an intermittent communication buss, power supply, ground or internal module malfunction.
5. This step tests for the correct power supply conditions of the suspect module or modules.
6. his step identifies which of the GMLAN busses the module or modules use for communication. Use the Data Link References for identifying the correct buss to analyze.
11. The module which was not communicating due to an open in the GMLAN serial data circuits may have set Loss of Communication DTCs for those modules that it was monitoring.
20. he modules which can communicate indicate the module which cannot communicate. You must clear the DTC from these modules to avoid future misdiagnosis.