Toyota Tacoma 2015-2018 Service Manual: Brake Warning Light Remains ON

Toyota Tacoma 2015-2018 Service Manual / Brake Control / Dynamic Control Systems / Vehicle Stability Control System(for Hydraulic Brake Booster) / Brake Warning Light Remains ON

DESCRIPTION

The BRAKE warning light comes on when brake fluid is insufficient, the parking brake is applied or the EBD is defective.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

When replacing the skid control ECU (master cylinder solenoid), perform calibration (See page ).
Inspect the fuses for circuits related to this system before performing the following inspection procedure.

PROCEDURE

1.	CHECK THAT SKID CONTROL ECU CONNECTOR SECURELY CONNECTED

(a) Check the skid control ECU (master cylinder solenoid) connector connection.

OK:

The connector is securely connected.

CONNECT CONNECTOR TO ECU CORRECTLY

CHECK DTC

(a) Check for DTCs (See page Result ).

Result

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

REPAIR CIRCUITS INDICATED BY OUTPUT DTCS

3.	INSPECT BATTERY

(a) Inspect the battery voltage (See page Standard voltage: ).

Standard voltage:

11 to 14 V

CHECK CHARGING SYSTEM

4.	CHECK BRAKE FLUID LEVEL

(a) Turn the ignition switch off.

(b) Depress the brake pedal 20 times or more (until the pedal reaction feels light and pedal stroke becomes longer).

HINT:

When the ignition switch is turned to ON, brake fluid is sent to the accumulator and the fluid level decreases by approximately 5 mm (0.197 in.) from the level when the ignition switch is off (normal).

OK:

Brake fluid level is normal.

CHECK AND REPAIR BRAKE FLUID LEAKAGE

5.	CHECK CAN COMMUNICATION SYSTEM

(a) Turn the ignition switch off.

(b) Connect the Techstream to the DLC3.

(d) Turn the Techstream on.

(e) Select CAN Bus Check from the System Selection Menu screen and follow the prompts on the screen to inspect the CAN bus (See page OK: OK: ).

OK:

CAN Bus Check indicates no malfunctions in CAN communication.

GO TO CAN COMMUNICATION SYSTEM (HOW TO PROCEED WITH TROUBLESHOOTING)

6.	PERFORM ACTIVE TEST USING TECHSTREAM (BRAKE WARNING LIGHT)

(a) Turn the ignition switch off.

(b) Connect the Techstream to the DLC3.

(d) Turn the Techstream on.

(e) Enter the following menus: ABS/VSC/TRAC / Active Test.

(f) According to the display on the Techstream, perform the Active Test.

ABS/VSC/TRAC

Tester Display	Test Part	Control Range	Diagnostic Note
Brake Warning Light	Brake warning light	Warning light OFF/ON	Observe the combination meter. [Vehicle condition] Vehicle stopped

(g) Check the Techstream display condition of the brake warning light.

Result

Result	Proceed to
Display of the Data List remains OFF	A
Display of the Data List remains ON	B

GO TO METER / GAUGE SYSTEM

7.	CHECK HARNESS AND CONNECTOR (IG1 TERMINAL)

(a) Disconnect the skid control ECU connector (master cylinder solenoid).

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

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
S1-46 (IG1) - Body ground	Ignition switch ON	11 to 14 V

Text in Illustration

*a	Front view of wire harness connector (to Skid Control ECU (Master Cylinder Solenoid))

REPAIR OR REPLACE HARNESS OR CONNECTOR

8.	CHECK HARNESS AND CONNECTOR (GND TERMINAL)

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
S1-1 (GND1) - Body ground	Always	Below 1 Ω
S1-32 (GND2) - Body ground	Always	Below 1 Ω
S2-4 (GND3) - Body ground	Always	Below 1 Ω

Text in Illustration

*a	Front view of wire harness connector (to Skid Control ECU (Master Cylinder Solenoid))

(b) Reconnect the skid control ECU (master cylinder solenoid) connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR

9.	INSPECT BRAKE FLUID LEVEL WARNING SWITCH

(a) Disconnect the B2 brake fluid level warning switch (brake master cylinder reservoir sub-assembly) connector.

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

Standard Resistance:

Tester Connection	Switch Condition	Specified Condition
1 - 2	Float UP (Switch off)	1.9 to 2.1 kΩ
1 - 2	Float DOWN (Switch on)	Below 1 Ω

Text in Illustration

*a	Component without harness connected (Brake Fluid Level Warning Switch (Brake Master Cylinder Reservoir Sub-assembly))

REPLACE BRAKE MASTER CYLINDER SUB-ASSEMBLY (BRAKE FLUID LEVEL WARNING SWITCH)

10.	CHECK HARNESS AND CONNECTOR (SKID CONTROL ECU - BRAKE FLUID LEVEL WARNING SWITCH)

(a) Disconnect the S1 skid control ECU (master cylinder solenoid) connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
S1-41 (LBL) - B2-2	Always	Below 1 Ω
S1-41 (LBL) - Body ground	Always	10 kΩ or higher
B2-1 - Body ground	Always	Below 1 Ω

REPLACE MASTER CYLINDER SOLENOID

REPAIR OR REPLACE HARNESS OR CONNECTOR

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