Circuit Description
The transmission control module (TCM) can be calibrated to communicate with an electronically controlled engine via SAE J1939. Diagnostic information is also communicated via SAE J1939. This DTC applies to the 6.6L engine only.
DTC U2105 is a type B DTC.
Conditions for Running the DTC
| • | The components are powered and ignition voltage is greater than 9 volts and less than 18 volts. |
| • | Engine speed is greater than 200 RPM and less than 7,500 RPM for 5 seconds. |
Conditions for Setting the DTC
DTC U2105 sets when the TCM detects one of the following conditions:
| • | The TCM is calibrated for J1939 communication and the TCM detects an error on the controller area network (CAN) link. No engine throttle or torque messages for 3 seconds. |
| • | An open at the CAN backbone, such as a missing resistor or an open connection. |
Action Taken When the DTC Sets
| • | DTC U2105 is stored in the TCM history. |
| • | The malfunction indicator lamp (MIL) illuminates on the second occurrence. |
| • | The TCM uses the default throttle value. |
| • | The TCM halts shift adapts. |
| • | The TCM inhibits torque converter clutch (TCC) engagement. |
Conditions for Clearing the MIL/DTC
A scan tool can clear the code from the TCM history. The TCM automatically clears the DTC from the TCM history if the vehicle completes 40 warm-up cycles without failure.
Diagnostic Aids
| • | Inspect the wiring for poor electrical connections at the TCM. Look for the following conditions: |
| - | A bent terminal |
| - | A backed-out terminal |
| - | A damaged terminal |
| - | Poor terminal tension |
| - | A chafed wire |
| - | A broken wire inside the insulation |
| • | When diagnosing for an intermittent short or open, massage the wiring harness while watching the test equipment for a change. |
| • | You may have to drive the vehicle in order to experience a fault. |
| • | If this DTC is present in a new vehicle, harsh shifting may occur since shift adaptive action is inhibited. |
| • | In certain applications, vehicle cruise control function may be used to verify if J1939 is operating properly. If this function is not operating, the engine controller may not be broadcasting a J1939 signal. This could be due to incorrect parameter setting at the ECU or a defective ECU. The vehicle OEM should be contacted to verify proper ECU setting. |
| • | Intermittent cycling of the TCC could indicate that a J1939 wiring problem exists. It is possible to have an open condition in the J1939 wiring and U2105 not set or only set when an open condition at the J1939 is present over the period of time needed to allow the U2105 to set. |
| • | It is necessary to have two 120 ohm resistors installed in the J1939 CAN. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This step checks for loose CAN connectors.
-
This step checks resistance between pin 29 and 32 on the C1 connector.
Step | Action | Value | Yes | No |
|---|---|---|---|---|
Schematic Reference: Automatic Transmission Controls Schematics | ||||
1 | Did you perform the Diagnostic System Check - Automatic Transmission? | -- | Go to Step 2 | |
Did you find any loose connectors? | -- | Go to Step 3 | Go to Step 4 | |
3 |
IMPORTANT: The vehicle OEM has responsibility for all external wiring and should perform all vehicle harness repairs. Harness repair performed by ATD distributors and dealers is not covered under ATD warranty. Proper OEM authorization is required for ATD distributors and dealers to recover harness repair cost. Repair the vehicle J1939 CAN wiring harness. Did you complete the repair? | -- | Go to Step 6 | Go to Step 4 |
Is the resistance greater than the specified value? | 60 ohms | Go to Step 5 | Go to Step 6 | |
5 | Return the vehicle to OEM for repair. A resistance reading greater than 60 ohms usually indicates that a terminating resistor is missing. There should be two 120 ohms resistors wired parallel in the J1939 CAN. Did you complete the repair? | -- | Go to Step 6 | -- |
6 | Perform the following procedure In order to verify the repair:
Did the DTC return? | -- | Go to Step 1 | System OK |
