DTC U0100: Lost Communication with ECM / PCM "A" [10/2014 - 10/2015]: Procedure

1. Disconnect the ECM connector.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

2. Turn the engine switch on (IG).
3. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   A18-2 (+B) - Body ground	Engine switch on (IG)	11 to 14 V
   A18-3 (+B2) - Body ground	Engine switch on (IG)	11 to 14 V

   TEXT IN ILLUSTRATION
   
   

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

Result: 

NG 

GO TO ECM POWER SOURCE CIRCUIT 

(Refer to ECM Power Source Circuit [10/2014 - ] )

Result: 

OK 

See step  2

1. Turn the engine switch off.
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
   B10-49 (E1) - Body ground	Always	Below 1 Ω

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  3

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
   B2-6 (CAN+) - B10-31 (CAN+)	Always	Below 1 Ω
   B2-7 (CAN-) - B10-1 (CAN-)	Always	Below 1 Ω
   B2-6 (CAN+) or B10-31 (CAN+) - Body ground and other terminals	Always	10 kΩ or higher
   B2-7 (CAN-) or B10-1 (CAN-) - Body ground and other terminals	Always	10 kΩ or higher

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  4

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

   Result

   Display (DTC Output)	Proceed to
   U0100	A
   No DTC	B

Result: 

A 

REPLACE ECM 

(Refer to COMPONENTS [10/2014 - ] )

Result: 

B 

REPLACE TCM 

(Refer to COMPONENTS [10/2014 - ] )