DTC U0100: Lost Communication with ECM / PCM "A" [12/2013 - 11/2016]: Procedure

1. Disconnect the TCM connector.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Front view of wire harness connector (to TCM)

2. Turn the ignition switch to ON.
3. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   C3-18 (+B) - C3-8 (E1)	Ignition switch ON	9 to 14 V

4. Turn the ignition switch off.
5. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   C3-8 (E1) - Body ground	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result:  2

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result:  1

OK 

See step  2

1. Disconnect the TCM connector.
2. Disconnect the ECM connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   C3-6 (CAN+) - C1-31 (CAN+)	Always	Below 1 Ω
   C3-7 (CAN-) - C1-1 (CAN-)	Always	Below 1 Ω
   C3-6 (CAN+) or C1-31 (CAN+) - Body ground and other terminals	Always	10 kΩ or higher
   C3-7 (CAN-) or C1-1 (CAN-) - Body ground and other terminals	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result:  2

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result:  1

OK 

See step  3

1. Connect the Techstream to the DLC3.
2. Clear the DTCs.

   Powertrain > ECT > Clear DTCs 

3. Replace the TCM.

   HINT: 

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

4. Start the engine.
5. Read the DTCs.

   Powertrain > ECT > Trouble Codes 

   Result

   Result	Proceed to
   DTC U0100 is output	A
   DTCs are not output	B

Result:  1

A 

REPLACE ECM. Refer to  COMPONENTS [12/2013 - 11/2016] 

Result:  2

B 

REPLACE TCM. Refer to  COMPONENTS [12/2013 - 11/2016]