DTC C1378/44: Capacitor Communication Malfunction: Procedure

1. Make sure that there is no looseness at the locking part and the connecting part of the connector.
   Fig 1: Identifying Brake Control Power Supply Connector Terminals

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2. Disconnect the brake control power supply connector.
3. Turn the ignition switch to ON.
4. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   O40-5 (IG1) - Body ground	Ignition switch ON	11 to 14 V

   TEXT IN ILLUSTRATION
   
   

   *1	Front view of wire harness connector (to Brake Control Power Supply)

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR (IG1 CIRCUIT) 

OK: Go to next step 

1. Turn the ignition switch off.
   Fig 2: Identifying Brake Control Power Supply Connector Terminals

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   O40-14 (GND) - Body ground	Always	Below 1 Ω

   TEXT IN ILLUSTRATION
   
   

   *1	Front view of wire harness connector (to Brake Control Power Supply)

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR (GND CIRCUIT) 

OK: Go to next step 

1. Make sure that there is no looseness at the locking part and the connecting part of the connector.
   Fig 3: Identifying Skid Control ECU Connector Terminals

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. Disconnect the A44 and A47 skid control ECU connectors.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A44-20 (ENA) - O40-12 (ENA)	Always	Below 1 Ω
   A44-20 (ENA) - Body ground	Always	10 kΩ or higher
   A47-30 (FAIL) - O40-13 (FAIL)	Always	Below 1 Ω
   A47-30 (FAIL) - Body ground	Always	10 kΩ or higher

   TEXT IN ILLUSTRATION
   
   

   *1	Front view of wire harness connector (to Skid Control ECU)
   *2	Front view of wire harness connector (to Brake Control Power Supply)

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Reconnect the skid control ECU connectors and the brake control power supply connector.
2. Clear the DTCs, refer to DTC CHECK / CLEAR .
3. Turn the ignition switch to ON.
4. Check if the same DTC is recorded, refer to DTC CHECK / CLEAR .

   Result

   Result	Proceed to
   DTC (C1378/44) is output	A
   DTC (C1378/44) is not output	B

B → See step   7 

A: Go to next step 

1. Check the INF code from the Freeze Frame Data memorized when the DTC (C1378/44) was stored, refer to FREEZE FRAME DATA .

   Result

   Result	Proceed to
   INF code (112) is not output	A
   INF code (112) is output	B

B → See step   8 

A → See step   6