DTC U0100: Lost Communication with ECM / PCM "A": Procedure

1. Disconnect the cable from the negative (-) battery terminal before measuring the resistances of the CAN main wire and CAN branch wire.
   WARNING:

   Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to disable the SRS system.

   NOTE:

   When disconnecting the cable, some systems need to be initialized after the cable is reconnected, refer to INITIALIZATION .

NEXT: Go to next step 

1. Disconnect the A67 ECM connector.
   Fig 1: Identifying A67 ECM Connector Terminal

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Switch Condition	Specified Condition
   A67-13 (CAN+) - A67-26 (CAN-)	Ignition switch off	108 to 132 Ω

   TEXT IN ILLUSTRATION
   
   

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

NG → REPAIR OR REPLACE ECM CAN MAIN WIRE OR CONNECTOR (CAN+, CAN-) 

OK: Go to next step 

1. Connect the cable to the negative (-) battery terminal.
   NOTE:

   When disconnecting the cable, some systems need to be initialized after the cable is reconnected, refer to INITIALIZATION .

   Fig 2: Identifying B57 ECM Battery Connector & A67 ECM Battery Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   TEXT IN ILLUSTRATION
   
   

   *a

   Front view of wire harness connector (to ECM)

   -

   -

2. Disconnect the B57 ECM connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A67-14 (EC) - Body ground	Always	Below 1 Ω
   B57-46 (E1) - Body ground	Always	Below 1 Ω
   B57-57 (E01) - Body ground	Always	Below 1 Ω
   B57-58 (E02) - Body ground	Always	Below 1 Ω
   B57-60 (ME01) - Body ground	Always	Below 1 Ω

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

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   A67-15 (BATT) - Body ground	Always	11 to 14 V
   A67-3 (+B) - Body ground	Battery positive (+) voltage applied to terminal A67-21 (MREL)	11 to 14 V
   A67-4 (+B2) - Body ground	Battery positive (+) voltage applied to terminal A67-21 (MREL)	11 to 14 V

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK → See step   4