DTC U0101: Lost Communication with TCM: Procedure

1. Connect the Techstream to the DLC3.
2. Turn the ignition switch to ON.
3. Turn the Techstream on.
4. Enter the following menus: Powertrain / Engine / Trouble Code.
5. Read the DTCs.

   Result

   Display (DTC output)	Proceed to
   U0101	A
   U0101 and other DTCs	B

B → See step   2 

A: Go to next step 

1. Disconnect the TCM connector.
   Fig 1: Checking ECU Terminal Voltage (+B And E1 Terminals)

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Turn the ignition switch to ON.
3. Measure the voltage of the TCM connectors.

   Standard voltage

   Tester Connection	Condition	Specified Condition
   C56-18 (+B) - C56-8 (E1)	Ignition switch ON	11 to 14 V

4. Turn the ignition switch off.
5. Measure the resistance of the TCM connector.

   Standard resistance

   Tester Connection	Condition	Specified Condition
   C56-8 (E1) - Body ground	Always	Below 1 Ω

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Disconnect the TCM connector.
   Fig 2: Identifying C56 TCM Connector And C55 ECM Connector

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Disconnect the ECM connector.
3. Measure the resistance of the wire harness side connectors.

   Standard resistance

   Tester Connection	Condition	Specified Condition
   C56-6 (CAN+) - C55-2 (CAN+)	Always	Below 1 Ω
   C56-7 (CAN-) - C55-1 (CAN-)	Always	Below 1 Ω
   C56-6 (CAN+) or C55-2 (CAN+) - Body ground	Always	1 MΩ or more
   C56-7 (CAN-) or C55-1 (CAN-) - Body ground	Always	1 MΩ or more

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Replace the ECM. Refer to REMOVAL .
   NOTE:

   Replace the ECM with a ECM from a normally functioning vehicle of the same model.

NEXT: Go to next step 

1. Connect the Techstream to the DLC3.
2. Clear the DTC. Refer to DTC CHECK / CLEAR .
3. Start the engine.
4. Read the DTCs.

   Result

   Display (DTC Output)	Proceed to
   U0101	A
   No DTC	B

B → END 

A → See step   7