Lexus NX: Brake Override System

DESCRIPTION

When the vehicle is being driven with the accelerator pedal depressed, depressing the brake pedal without releasing the accelerator pedal will activate the brake override system to restrict driving torque. The conditions for activating the brake override system as well as the items that are controlled are explained below.

Activation Conditions:

Items Controlled:

Deactivation Conditions:

CAUTION / NOTICE / HINT

Inspection Method

Drive at 10 km/h (6 mph), depress the accelerator pedal by 1/2 to 3/4 and keep it in that position. Under these conditions, if driving torque is controlled when the brake pedal is depressed by the left foot of the driver, it can be confirmed that the brake override system has operated.

CAUTION:

Perform this road test only in an appropriate safe location, in accordance with all local laws.

Pay careful attention to the surroundings when performing the road test.

HINT:

The brake override system restricts driving torque if the brake pedal is depressed when driving with the accelerator pedal depressed. If a customer reports experiencing a loss of power (driving torque) after the accelerator and brake pedals have both been intentionally depressed, explain that this is not a malfunction, and depressing both the accelerator and brake pedals at the same time should be avoided.

PROCEDURE

1.	CHECK DTC OUTPUT (HEALTH CHECK)

(a) Connect the Techstream to the DLC3.

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

(c) Enter the following menus: System Select / Health Check.

(d) Check for DTCs.

(e) Turn the power switch off.

DTCs are output.

GO TO DTC CHART

No DTCs are output.

2.	READ VALUE USING TECHSTREAM (MASTER CYLINDER CTRL TRQ)

(a) Connect the Techstream to the DLC3.

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

(c) Enter the following menus: Powertrain / Hybrid Control / Data List / Master Cylinder Ctrl Trq.

Powertrain > Hybrid Control > Data List

Tester Display
Master Cylinder Ctrl Trq

Powertrain > Hybrid Control > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Master Cylinder Ctrl Trq	Braking torque equivalent to master cylinder brake fluid pressure Total braking torque Master cylinder brake fluid pressure control torque = hydraulic brake control torque + rear regenerative brake torque*	-	Brake pedal depressed: Changes with the brake pedal pressure	Master cylinder pressure sensor

Result	Proceed to
Display changes according to brake pedal depression force.	A
Display does not change according to brake pedal depression force.	B

(d) Turn the power switch off.

B

CHECK BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

A

3.	READ VALUE USING TECHSTREAM (ACCEL PEDAL POS #1, ACCEL PEDAL POS #2)

(a) Connect the Techstream to the DLC3.

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

(c) Enter the following menus: Powertrain / Hybrid Control / Data List / Accel Pedal Pos #1, Accel Pedal Pos #2.

Powertrain > Hybrid Control > Data List

Tester Display
Accel Pedal Pos #1
Accel Pedal Pos #2

(d) Read the value of "Accel Pedal Pos #1" and "Accel Pedal Pos #2" displayed on the Techstream.

Standard:

Inspection Condition	Specified Condition
Accelerator pedal fully released → fully depressed	Value (%) changes with accelerator pedal operation

HINT:

Refer to the SFI system Data List for the "Accel Pedal Pos #1" and "Accel Pedal Pos #2" standard ranges when the accelerator pedal is operated.

Click here

(e) Turn the power switch off.

NG

REPLACE ACCELERATOR PEDAL(W/SENSOR) ROD ASSEMBLY

OK

4.	READ VALUE USING TECHSTREAM (VEHICLE SPD)

(a) Connect the Techstream to the DLC3.

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

(c) Enter the following menus: Powertrain / Hybrid Control / Data List / Vehicle Spd.

Powertrain > Hybrid Control > Data List

Tester Display
Vehicle Spd

(d) Read the value of "Vehicle Spd" displayed on the Techstream.

Standard:

Inspection Condition	Specified Condition
Vehicle stopped	0 km/h (0 mph)
Vehicle being driven at a constant speed (16 to 64 km/h (10 to 40 mph))	No large fluctuations in displayed speed

CAUTION:

Perform this road test only in an appropriate safe location, in accordance with all local laws.

HINT:

Data can be captured relatively easily by using the snapshot function in the Data List. Confirm the data after performing the drive test.

(e) Turn the power switch off.

NG

GO TO METER / GAUGE SYSTEM

OK

5.	READ VALUE USING TECHSTREAM (FR, FL, RR, RL WHEEL SPEED)

(a) Connect the Techstream to the DLC3.

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

(c) Enter the following menus: Chassis / ABS/VSC/TRC / Data List / All Data / FR Wheel Speed, FL Wheel Speed, RR Wheel Speed and RL Wheel Speed.

Chassis > ABS/VSC/TRC > Data List

Tester Display
FR Wheel Speed
FL Wheel Speed
RR Wheel Speed
RL Wheel Speed

(d) Read the value of "FR Wheel Speed", "FL Wheel Speed", "RR Wheel Speed" and "RL Wheel Speed" displayed on the Techstream.

Standard:

Inspection Condition	Specified Condition
Vehicle stopped	0 km/h (0 mph)
Vehicle being driven at a constant speed (16 to 64 km/h (10 to 40 mph))	No large fluctuations in displayed speed

CAUTION:

Perform this road test only in an appropriate safe location, in accordance with all local laws.

HINT:

Data can be captured relatively easily by using the snapshot function in the Data List. Confirm the data after performing the drive test.

(e) Turn the power switch off.

OK

END

NG

INSPECT SPEED SENSOR (FRONT OR REAR SPEED SENSOR)

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