DTC C146C: Open Circuit in ABS Motor Relay Circuit; DTC C146D: Short Circuit in ABS Motor Relay Circuit [10/2018 - ]: Procedure

1. Make sure that there is no looseness at the locking part and the connecting part of the connector.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Front view of wire harness connector (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

   OK

   The connector is securely connected.

2. Disconnect the A37 skid control ECU (brake booster with master cylinder assembly) connector.
3. Check both the connector case and the terminals for deformation and corrosion.

   OK

   No deformation or corrosion.

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

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   A37-41 (BM) - Body ground	Always	11 to 14 V

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR (BM CIRCUIT) 

Result: 

OK 

See step  2

1. Make sure that there is no looseness at the locking part and the connecting part of the connector.

   OK

   The connector is securely connected.

2. Disconnect the A48 brake actuator assembly connector.
3. Check both the connector case and the terminals for deformation and corrosion.

   OK

   No deformation or corrosion.

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A37-40 (+BM) - A48-10 (+BM)	Always	Below 1 Ω
   A37-40 (+BM) or A48-10 (+BM) - Body ground	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

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
   A48-1 (MGND) - Body ground	Always	Below 1 Ω

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Front view of wire harness connector (to Brake Actuator Assembly)

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR (GND CIRCUIT) 

Result: 

OK 

See step  4

1. Reconnect the A37 skid control ECU (brake booster with master cylinder assembly) connector.
2. Reconnect the A48 brake actuator assembly connector.
3. Clear the DTCs.

   Refer to DTC CHECK / CLEAR [10/2018 - ]

   Chassis > ABS/VSC/TRAC > Clear DTCs 

4. Turn the power switch off.
5. Turn the power switch on (READY).
6. Perform a road test.
7. Check if the same DTC is output.

   Refer to DTC CHECK / CLEAR [10/2018 - ]

   Chassis > ABS/VSC/TRAC > Trouble Codes 

   Result

   Result	Proceed to
   DTCs C146C and C146D are not output.	A
   DTCs C146C and/or C146D are output.	B

   HINT: 

   • If a speed signal of 20 km/h (12 mph) or more is sent to the skid control ECU (brake booster with master cylinder assembly) with the power switch on (IG) and the stop light switch assembly off, the ECU performs self-diagnosis of the motor and solenoid circuits.
   • If the normal system code is output (no DTCs are output), slightly jiggle the connectors, wire harness, and fuses of the skid control ECU (brake booster with master cylinder assembly).
   • If any DTCs are output while jiggling a connector or wire harness from the skid control ECU (brake booster with master cylinder assembly), inspect and repair the connector or wire harness.
   • The DTCs were probably output due to a bad connection of the connector terminal.

Result: 

A 

USE SIMULATION METHOD TO CHECK. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [10/2018 - ] 

Result: 

B 

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY. Refer to  REMOVAL [10/2018 - 07/2022]  , or refer to  REMOVAL [07/2022 - ]