DTC C1377: Capacitor Malfunction [10/2020 - 10/2023]: Procedure

1. Check the INF code from the Freeze Frame Data stored when DTC (C1377) was stored.

   Refer to FREEZE FRAME DATA [10/2020 - 10/2023]

   Chassis > ABS/VSC/TRAC > DTC (C1377) > Freeze Frame Data 

   Tester Display
   Detailed Freeze DTC

   Result

   Result	Proceed to
   INF codes 109 and/or 110 are output.	A
   INF codes 101, 102, 105, 106 and/or 108 are output.	B
   INF code 103 is output.	C

Result: 

B 

REPLACE BRAKE CONTROL POWER SUPPLY WITH BRACKET ASSEMBLY. Refer to  REMOVAL [10/2020 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023] 

Result: 

C 

See step  7

Result: 

A 

See step  2

1. Make sure that there is no looseness at the locking part and the connecting part of the connector.
2. Disconnect the L101 brake control power supply with bracket assembly connector.
3. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   L101-5 (+BC) - Body ground	Always	11 to 14 V

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR (+BC CIRCUIT) 

Result: 

OK 

See step  3

1. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   L101-8 (GND) - Body ground	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR (GND CIRCUIT) 

Result: 

OK 

See step  4

1. Reconnect the L101 brake control power supply with bracket assembly connector.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Component with harness connected (Brake Control Power Supply with Bracket Assembly)

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

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   L101-1 (OUT1) - Body ground	Power switch on (IG)	11 to 14 V
   L101-4 (OUT2) - Body ground	Power switch on (IG)	11 to 14 V

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE BRAKE CONTROL POWER SUPPLY WITH BRACKET ASSEMBLY. Refer to  REMOVAL [10/2020 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023] 

Result: 

OK 

See step  5

1. Turn the power switch on (IG).

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Component with harness connected (Skid Control ECU Assembly)

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

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   A11-7 (CBI1) - Body ground	Power switch on (IG)	8.8 to 14 V
   A12-2 (CBI2) - Body ground	Power switch on (IG)	8.8 to 14 V

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE SKID CONTROL ECU ASSEMBLY. Refer to  REMOVAL [10/2020 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023] 

Result: 

OK 

See step  6

1. Turn the power switch off.
2. Clear the DTCs.

   Refer to DTC CHECK / CLEAR [10/2020 - 10/2023]

   Chassis > ABS/VSC/TRAC > Clear DTCs 

3. Turn the power switch off.
4. Turn the power switch on (IG).
5. Check if the same DTC is output.

   Refer to DTC CHECK / CLEAR [10/2020 - 10/2023]

   Chassis > ABS/VSC/TRAC > Trouble Codes 

   Result

   Result	Proceed to
   DTC C1377 is not output.	A
   DTC C1377 is output.	B

Result: 

A 

USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [10/2020 - 11/2021]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [11/2021 - 10/2022]  , or refer to  HOW TO PROCEED WITH TROUBLESHOOTING [10/2022 - 10/2023] 

Result: 

B 

REPLACE SKID CONTROL ECU ASSEMBLY. Refer to  REMOVAL [10/2020 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023] 

1. Check the auxiliary battery voltage.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   Auxiliary battery	Power switch on (IG)	11 to 14 V
   Auxiliary battery	Power switch on (READY)	11 to 15.5 V

   Result

   Proceed to
   OK
   NG

Result: 

NG 

CHARGE OR REPLACE AUXILIARY BATTERY 

Result: 

OK 

See step  8

1. Make sure that there is no looseness at the locking part and the connecting part of the connector.
2. Disconnect the L101 brake control power supply with bracket assembly connector.
3. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   L101-5 (+BC) - Body ground	Always	11 to 14 V

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR (+BC CIRCUIT) 

Result: 

OK 

See step  9

1. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   L101-8 (GND) - Body ground	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE BRAKE CONTROL POWER SUPPLY WITH BRACKET ASSEMBLY. Refer to  REMOVAL [10/2020 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023] 

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR (GND CIRCUIT)