Lost Communication with TCM (U0101)

The Transmission Control Module (TCM) and ECM perform 2-way communication with each other via the Controller Area Network (CAN). The TCM sends signals to the ECM concerning required engine speed, required engine torque, warning indicators in the combination meter, DTCs and other data. The ECM sends signals to the TCM concerning engine speed, opening angle of the throttle valve, temperature of intake air, temperature of engine coolant, engine torque and other data. If the TCM cannot communicate with the ECM, the TCM will conclude that there is a malfunction in the CAN system, illuminate the MIL and set a DTC.

1. 1
   Connect the Techstream to the DLC3.
2. 2
   Turn the ignition switch to ON and turn the Techstream on.
3. 3
   Clear the DTCs (even if no DTCs are stored, perform the Clear DTC procedure) (See page ).
4. 4
   Turn the ignition switch off and wait for at least 30 seconds.
5. 5
   Turn the ignition switch to ON and turn the Techstream on.
6. 6
   Wait 5 seconds or more.
7. 7
   Enter the following menus: Powertrain / Engine / Trouble Codes.
8. 8
   Read the Pending DTCs.

   HINT:

   • If a pending DTC is output, the system is malfunctioning.
   • If a pending DTC is not output, perform the following procedure.
9. 9
   Enter the following menus: Powertrain / Engine / Utility / All Readiness.
10. 10
    Input the DTC: U0101.
11. 11
    Check the DTC judgment result.

    Techstream Display	Description
    NORMAL	DTC judgment completed System normal
    ABNORMAL	DTC judgment completed System abnormal
    INCOMPLETE	DTC judgment not completed Perform driving pattern after confirming DTC enabling conditions
    N/A	Unable to perform DTC judgment Number of DTCs which do not fulfill DTC preconditions has reached ECU's memory limit

    HINT:

    • If the judgment result shows NORMAL, the system is normal.
    • If the judgment result shows ABNORMAL, the system has a malfunction.
12. 12
    If the test result is INCOMPLETE or N/A and no pending DTC is output, perform a universal trip and check for permanent DTCs (See page ).
    

    HINT:

    • If a permanent DTC is output, the system is malfunctioning.
    • If no permanent DTC is output, the system is normal.

NOTICE:

Inspect the fuses for circuits related to this system before performing the following inspection procedure.

HINT:

Read freeze frame data using the Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can help determine if the vehicle was moving or stationary, if the engine was warmed up or not, if the air fuel ratio was lean or rich, and other data from the time the malfunction occurred.

1. CHECK OTHER DTC OUTPUT (IN ADDITION TO DTC U0101)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Enter the following menus: System Select / Health Check.

(e) Read the DTCs.

HINT:

If any DTCs other than U0101 are output, troubleshoot those DTCs first.

B

GO TO DTC CHART

A

1. INSPECT ECU POWER SOURCE CIRCUIT (TCM POWER SOURCE)

(a) Disconnect the TCM connector.

(b) Turn the Ignition switch to ON.

(c) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

B

GO TO TCM POWER SOURCE CIRCUIT

C

GO TO TCM POWER SOURCE CIRCUIT

A

1. CHECK HARNESS AND CONNECTOR (ECM - TCM)

(a) Disconnect the TCM connector.

(b) Disconnect the ECM connector.

(c) Measure the resistance according to the value(s) in the table below.

Standard Resistance (Check for Open):

Standard Resistance (Check for Short):

B

GO TO STEP 5

C

REPAIR OR REPLACE HARNESS OR CONNECTOR (ECM - TCM)

A

1. REPLACE TCM

(a) Replace the TCM (for U760E) (See page
).

NEXT

GO TO STEP 6

1. REPLACE TCM

(a) Replace the TCM (for U760F) (See page
).

NEXT

1. CHECK WHETHER DTC OUTPUT RECURS (DTC U0101)

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Turn the Techstream on.

(d) Enter the following menus: Powertrain / Engine / Trouble Codes.

(e) Read the DTCs.

A

END

B

REPLACE ECM