4L30-E Automatic Transmission

Circuit Description
The Controller Area Network (CAN) is used to receive and transmit data (signal) between Engine Control Module (ECM), the Electronic Brake/Traction Control Module (EBTCM) and the Transmission Control Module (TCM). The data is constantly being sent back and forth between the modules transferring information from their different inputs, reporting state-of-health, and supplying status messaging. Each module sends signals by toggling the circuit either high or low to produce pulse-width signals which the module decodes. Circuits XR888 and XY888 are the CAN information lines used to transmit the data between the modules.

When the TCM has not received an EBTCM data signal for a specified amount of time, then DTC U2108 will set. DTC U2108 is a type D DTC.

Condition for Running the DTC
The ignition switch is in the RUN position.

Condition for Setting the DTC
The TCM has not received EBTCM messaging for 1 second.

Action Taken When the DTC Sets
^ The ECM records the operating conditions in the Failure Records at the time of the DTC request from the TCM.
^ The TCM memory stores the DTC at the time of the first failure.

Conditions for Clearing the DTC
^ A History DTC clears after forty consecutive warm-up cycles, if no failures are present by this diagnostic or any other emission related diagnostic.
^ The scan tool clears the DTC.

Diagnostic Aids
Use the J 35616-A connector test adapter kit for any test that requires probing the TCM harness connector or a component harness connector. Using this kit will prevent damage to the harness connector terminals.

Check for the following conditions:
^ Poor connections at the TCM or at the component. Inspect the harness connectors for any backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.
^ Damaged harness. Inspect the wiring harness for damage. If the harness appears to be OK, observe the scan tool while moving any related connectors and any wiring harnesses. A change in the display may help to locate the fault.

Test Description
The number below refers to the step number on the diagnostic table.
2. Performing this step verifies that an operational abnormality did not take place during TCM power-up, such as Electromagnetic Interference (EMI).