Brake Warning Light Remains ON [01/2019 - 09/2022]: Procedure

1. Check that all of the following conditions required for the brake warning light / red (malfunction) to turn off are met:
   • The brake warning light / yellow (minor malfunction) and ABS warning light are not illuminated.

     HINT: 

     If the brake warning light / yellow (minor malfunction) or ABS warning light remains illuminated, make sure that the conditions required for the brake warning light / yellow (minor malfunction) and ABS warning light to turn off are met.

   • The brake fluid level in the brake master cylinder reservoir assembly (brake booster with master cylinder assembly) is not low.

   Result

   Proceed to
   NEXT

Result: 

NEXT 

See step  2

1. Check if ABS, VSC and/or electronically controlled brake system DTCs are output.

   Refer to DTC CHECK / CLEAR [01/2019 - 09/2022]

   Chassis > ABS/VSC/TRAC > Trouble Codes 

   Result

   Result	Proceed to
   DTCs are not output.	A
   DTCs are output.	B

Result: 

B 

REPAIR CIRCUITS INDICATED BY OUTPUT DTCS. Refer to  DIAGNOSTIC TROUBLE CODE CHART [01/2019 - 04/2020]  , or refer to  DIAGNOSTIC TROUBLE CODE CHART [04/2020 - 09/2022] 

Result: 

A 

See step  3

1. Check if CAN communication system DTCs are output.

   Refer to DIAGNOSIS SYSTEM [01/2019 - 04/2020] , or refer to DIAGNOSIS SYSTEM [04/2020 - 09/2022]

   Result

   Result	Proceed to
   DTCs are not output.	A
   DTCs are output.	B

Result: 

B 

INSPECT CAN COMMUNICATION SYSTEM. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [01/2019 - 09/2022] 

Result: 

A 

See step  4

1. Check if the skid control ECU (brake booster with master cylinder assembly) connector is securely connected.

   OK

   The connector is securely connected.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

CONNECT CONNECTOR TO BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY CORRECTLY 

Result: 

OK 

See step  5

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  6

1. Turn the power switch off.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

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

   OK

   The connector is securely connected.

3. Disconnect the A48 skid control ECU (brake booster with master cylinder assembly) connector.
4. Check both the connector case and the terminals for deformation and corrosion.

   OK

   No deformation or corrosion.

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

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   A48-23 (IG1) - Body ground	Power switch on (IG)	11 to 14 V

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR (IG1 CIRCUIT) 

Result: 

OK 

See step  7

1. Turn the power switch off.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

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

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A48-26 (GND1) - Body ground	1 minute or more after disconnecting the cable from the negative (-) auxiliary battery terminal	Below 1 Ω
   A48-39 (GND2) - Body ground	1 minute or more after disconnecting the cable from the negative (-) auxiliary battery terminal	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR (GND CIRCUIT) 

Result: 

OK 

See step  8

1. Reconnect the A48 skid control ECU (brake booster with master cylinder assembly) connector.
2. Select the Data List on the Techstream.

   Refer to DATA LIST / ACTIVE TEST [01/2019 - 09/2022]

   Chassis > ABS/VSC/TRAC > Data List 

   Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
   Brake Warning Light	Brake warning light / red (malfunction)	ON or OFF	ON: Warning light on OFF: Warning light off	-

   Chassis > ABS/VSC/TRAC > Data List 

   Tester Display
   Brake Warning Light

3. Check the Techstream display condition of the brake warning light / red (malfunction).

   Result

   Result	Proceed to
   ON is displayed.	A
   OFF is displayed.	B

Result: 

A 

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY. Refer to  REMOVAL [01/2019 - 09/2022] 

Result: 

B 

INSPECT METER / GAUGE SYSTEM. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [01/2019 - 09/2022]