Lexus NX: Brake Control Warning Light Remains ON

DESCRIPTION

The skid control ECU (brake booster with master cylinder assembly) is connected to the combination meter assembly via CAN communication.

If the skid control ECU stores a DTC, the brake warning light / yellow (minor malfunction) comes on in the combination meter assembly.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

When replacing the skid control ECU (brake booster with master cylinder assembly), perform initialization and calibration of the linear solenoid valve.

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PROCEDURE

1.

CHECK CAN COMMUNICATION SYSTEM

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

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Result

Proceed to

DTCs are not output.

A

DTCs are output.

B

B

INSPECT CAN COMMUNICATION SYSTEM

A

2.

CHECK IF BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY CONNECTOR IS SECURELY CONNECTED

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

OK:

The connector is securely connected.

NG

CONNECT CONNECTOR TO BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY CORRECTLY

OK

3.

CHECK AUXILIARY BATTERY

(a) Check the auxiliary battery voltage.

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

Auxiliary battery

Power switch on (IG)

11 to 14 V

Auxiliary battery

Power switch on (READY)

11 to 15.5 V

NG

CHARGE OR REPLACE AUXILIARY BATTERY

OK

4.

READ VALUE USING TECHSTREAM (BRAKE WARNING LIGHT / YELLOW (MINOR MALFUNCTION))

(a) Connect the Techstream to the DLC3.

(b) Turn the power switch on (IG).

(c) Select the Data List on the Techstream.

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Chassis > ABS/VSC/TRAC > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

ECB Warning Light

Brake warning light / yellow (minor malfunction)

ON or OFF

ON: Warning light on

OFF: Warning light off

ECB: Electronically Controlled Brake System

Chassis > ABS/VSC/TRAC > Data List

Tester Display

ECB Warning Light

(d) Check the Techstream display condition of the brake warning light / yellow (minor malfunction).

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 BOOSTER WITH MASTER CYLINDER ASSEMBLY

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