Brake Warning Light Remains ON [12/2017 - 09/2018]: Procedure

1. Check if the skid control ECU (brake actuator assembly) connector is securely connected.

   OK

   The connector is securely connected.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

CONNECT CONNECTOR TO ECU CORRECTLY 

Result: 

OK 

See step  2

1. Check if CAN communication system DTCs are output.

   Refer to DIAGNOSIS SYSTEM [12/2017 - 09/2018]

   Result

   Proceed to
   DTC is not output
   DTC is output

Result: 

DTC is output 

CHECK CAN COMMUNICATION SYSTEM. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [12/2017 - 09/2018] 

Result: 

DTC is not output 

See step  3

1. Check the battery voltage.

   Standard voltage

   11 to 14 V

   Result

   Proceed to
   OK
   NG

Result: 

NG 

CHECK OR REPLACE CHARGING SYSTEM OR BATTERY. Refer to  ON-VEHICLE INSPECTION [12/2017 - 10/2020] 

Result: 

OK 

See step  4

1. Disconnect the A9 skid control ECU (brake actuator assembly) connector.
2. Turn the engine switch on (IG).
3. Measure the voltage according to the value(s) in the table below.

   Standard Voltage

   Tester Connection	Switch Condition	Specified Condition
   A9-12 (IG1) - Body ground	Engine 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  5

1. Turn the engine switch off.
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   A9-25 (GND1) - Body ground	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR (GND1 CIRCUIT) 

Result: 

OK 

See step  6

1. Turn the engine switch off.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Component without harness connected (Brake Fluid Level Warning Switch [Brake Master Cylinder Reservoir Assembly])

2. Remove the reservoir filler cap and strainer.
3. Disconnect the A18 brake fluid level warning switch (brake master cylinder reservoir assembly) connector.
4. Measure the resistance according to the value(s) in the table below.

   HINT: 

   A float is located inside the reservoir. Its position can be changed by increasing or decreasing the level of brake fluid.

   Standard Resistance

   Tester Connection	Switch Condition	Specified Condition
   A18-1 (+) - A18-2 (E)	Switch off (Float up)	10 kΩ or higher
   	Switch on (Float down)	Below 1 Ω

   HINT: 

   If there is no problem after finishing the above check, adjust the brake fluid level to the MAX level.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE BRAKE MASTER CYLINDER RESERVOIR ASSEMBLY. Refer to  REMOVAL [12/2017 - 10/2023] 

Result: 

OK 

See step  7

1. Disconnect the G34 combination meter assembly connector.
2. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   G34-17 (SW) or A18-1 (+) - Body ground	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  8

1. Reinstall the reservoir filler cap and strainer.
2. Reconnect the A18 brake fluid level warning switch (brake master cylinder reservoir assembly) connector.
3. Reconnect the G34 combination meter assembly connector.
4. Inspect the vacuum warning switch assembly.

   Refer to ON-VEHICLE INSPECTION [12/2017 - ]

   OK

   The vacuum warning switch assembly is normal.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPLACE VACUUM WARNING SWITCH ASSEMBLY. Refer to  REMOVAL [12/2017 - ] 

Result: 

OK 

See step  9

1. Disconnect the G34 combination meter assembly connector.
2. Disconnect the A4 vacuum warning switch assembly connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   G34-23 (IND) or A4-2 (+) - Body ground	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  10

1. Reconnect the A9 skid control ECU (brake actuator assembly) connector.
2. Reconnect the G34 combination meter assembly connector.
3. Reconnect the A4 vacuum warning switch assembly connector.
4. Connect the Techstream to the DLC3.
5. Turn the engine switch on (IG).
6. Turn the Techstream on.
7. Enter the following menus: Chassis / ABS/VSC/TRAC / Data List.
8. According to the display on the Techstream, read the Data List.

   Chassis > ABS/VSC/TRAC > Data List 

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

   Chassis > ABS/VSC/TRAC > Data List 

   Tester Display
   Brake Warning Light

9. Check the Techstream display condition of the brake system warning light (red indicator).

   Result

   Proceed to
   Display of the Data List remains OFF
   Display of the Data List remains ON

Result: 

Display of the Data List remains OFF 

INSPECT METER / GAUGE SYSTEM. Refer to  HOW TO PROCEED WITH TROUBLESHOOTING [12/2017 - 10/2023] 

Result: 

Display of the Data List remains ON 

REPLACE BRAKE ACTUATOR ASSEMBLY. Refer to  REMOVAL [12/2017 - 09/2018]