Toyota Tacoma manuals

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

DESCRIPTION

The skid control ECU (brake actuator assembly) is connected to the combination meter assembly via CAN communication.

If any of the following is detected, the brake warning light remains on:

  • The skid control ECU (brake actuator assembly) connector is disconnected from the skid control ECU (brake actuator assembly).
  • The brake fluid level is insufficient.
  • EBD operation is not possible.
  • The vacuum inside the brake booster decreases.*
    • *: for 2GR-FKS

WIRING DIAGRAM

CAUTION / NOTICE / HINT

CAUTION / NOTICE / HINT

NOTICE:

  • When replacing the skid control ECU (brake actuator assembly), perform zero point calibration and store system information (See page ).
  • Inspect the fuses for circuits related to this system before performing the following inspection procedure.

PROCEDURE

1.

CHECK CAN COMMUNICATION SYSTEM

(a) Check if CAN communication system DTCs are output (See page Result Result ).

Result

Result

Proceed to

DTC is not output

A

DTC is output

B

B

CHECK CAN COMMUNICATION SYSTEM

A

2.

CHECK IF BRAKE ACTUATOR ASSEMBLY CONNECTOR IS SECURELY CONNECTED

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

OK:

The connector is securely connected.

NG

CONNECT CONNECTOR TO BRAKE ACTUATOR ASSEMBLY CORRECTLY

OK

3.

INSPECT BATTERY

(a) Check the battery voltage.

Standard voltage:

11 to 14 V

NG

CHECK OR REPLACE CHARGING SYSTEM OR BATTERY

OK

4.

CHECK TERMINAL VOLTAGE (IG1 TERMINAL)

(a) Disconnect the skid control ECU (brake actuator assembly) connector.

(b) Turn the ignition switch to ON.

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

S1-12 (IG1) - Body ground

Ignition switch ON

11 to 14 V

Text in Illustration

*a

Front view of wire harness connector

(to Skid Control ECU [Brake Actuator Assembly])

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (IG1 CIRCUIT)

OK

5.

CHECK HARNESS AND CONNECTOR (GND1 TERMINAL)

(a) Turn the ignition switch off.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

S1-25 (GND1) - Body ground

Always

Below 1 Ω

Text in Illustration

*a

Front view of wire harness connector

(to Skid Control ECU [Brake Actuator Assembly])

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (GND1 CIRCUIT)

OK

6.

INSPECT BRAKE MASTER CYLINDER RESERVOIR ASSEMBLY

(a) Turn the ignition switch off.

(b) Remove the reservoir filler cap and strainer.

(c) Disconnect the A6 brake fluid level warning switch (brake master cylinder reservoir assembly) connector.

(d) 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

1 - 2

Switch off (Float up)

10 kΩ or higher

Switch on (Float down)

Below 1 Ω

Text in Illustration

*a

Component without harness connected

(Brake Fluid Level Warning Switch [Brake Master Cylinder Reservoir Assembly])

HINT:

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

NG

REPLACE BRAKE MASTER CYLINDER RESERVOIR ASSEMBLY

OK

7.

CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - BRAKE MASTER CYLINDER RESERVOIR ASSEMBLY)

(a) Disconnect the C9 combination meter assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

C9-28 (SW) - B2-1 (+)

Always

Below 1 Ω

B2-2 (E) - Body ground

Always

10 kΩ or higher

C9-28 (SW) or B2-1 (+) - Body ground

Always

10 kΩ or higher

Result

Result

Proceed to

OK (for 2GR-FKS)

A

OK (for 2TR-FE)

B

NG

C

B

GO TO STEP 10

C

REPAIR OR REPLACE HARNESS OR CONNECTOR

A

8.

INSPECT VACUUM WARNING SWITCH ASSEMBLY

(a) Remove the vacuum warning switch assembly (See page (b) Inspect the vacuum warning switch assembly (See page ).

(b) Inspect the vacuum warning switch assembly (See page OK: ).

OK:

The vacuum warning switch assembly is normal.

NG

REPLACE VACUUM WARNING SWITCH ASSEMBLY

OK

9.

CHECK HARNESS AND CONNECTOR (BRAKE WARNING LIGHT CIRCUIT)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

C9-28 (SW) - V12-2

Always

Below 1 Ω

V12-1 - Body ground

Always

Below 1 Ω

C9-9 (SW) or V12-2 - Body ground

Always

10 kΩ or higher

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

10.

READ VALUE USING TECHSTREAM (BRAKE WARNING LIGHT)

(a) Reinstall the reservoir filler cap and strainer.

(b) for 2GR-FKS

Reinstall the vacuum warning switch assembly.

(c) Reconnect the C9 combination meter assembly connector, S1 skid control ECU (brake actuator assembly) connector and the A6 brake fluid level warning switch (brake master cylinder reservoir assembly) connector.

(d) for 2GR-FKS

Reconnect the V12 vacuum warning switch assembly connector.

(e) Connect the Techstream to the DLC3.

(f) Turn the ignition switch to ON.

(g) Turn the Techstream on.

(h) Enter the following menus: Chassis / ABS/VSC/TRAC / Data List.

(i) According to the display on the Techstream, read the Data List.

ABS/VSC/TRAC

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Brake Warning Light

Brake warning light

OFF or ON

OFF: Warning light off

ON: Warning light on

-

(j) 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

A

INSPECT METER / GAUGE SYSTEM

B

REPLACE BRAKE ACTUATOR ASSEMBLY

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