U2106

DTC U2106

Circuit Description
The engine control module (ECM) and the transmission control module (TCM) communicate control and diagnostic information via a controller area network CAN) communication bus. The ECM monitors CAN operational status by expecting a constant flow of messages from the TCM. If the ECM fails to receive an expected message from the TCM, DTC U2104 or U2106 will set depending on what communication is lost.

Condition for Running the DTC
- The battery voltage is between 10-16 volts.
- The ignition switch is ON.

Condition for Setting the DTC
- The ECM detects that the CAN BUS reset counter is over run. (U2104)
- The ECM detects that CAN BUS messages from the TCM are not being received. (U2106)

Action Taken When the DTC Sets
- The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
- The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.

Condition for Clearing the DTC
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- Clear the MIL and the DTC with a scan tool.

Diagnostic Aids
If an intermittent condition is suspected, the following may cause an intermittent:
- Poor connections.
- Misrouted harness.
- Rubbed through wire insulation.
- Broken wire inside the insulation.

Check for the following conditions:
- Poor connection at ECM: Inspect harness connectors for 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 "DTC U2104" and "DTC U2106" display on the scan tool while moving connectors and wiring harness. A change in the display will indicate the location of the fault.

DTC U2104

Schematic Reference: Engine Controls Schematics

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