Circuit Description

WARNING: This page is about a different car, the 2005 Saturn L300. However, it is still accessible from the selected car via links, so may be relevant.

The controller area network (CAN) serial data line is a high speed serial data bus used to communicate information between the engine control module (ECM), body control module (BCM), and the transmission control module (TCM). Typical data-transmission speeds must be high enough to ensure that the required real-time response is maintained.

The CAN serial data line does not communicate with the scan tool via the data link connector (DLC). CAN serial data information is interpreted by the BCM and transmitted to the serial data line by the BCM.

Each module on the CAN serial data circuit learns the identity of the other modules on the circuit. If a module stops communicating after all modules have initiated for the ignition cycle, other modules set a DTC U21XX, where XX is equal to the 2 digit identification number specific for the module not communicating:

DTC U2105, can not communicate with the ECM
DTC U2106, can not communicate with the TCM
DTC U2107, can not communicate with the BCM

DTC U2105-U2199

Control Module	ID Number
Engine Control Module (ECM)	05
Transaxle Control Module (TCM)	06
Body Control Module (BCM)	07