Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Brake Switch "A" Circuit Short to Ground (P057111)

DESCRIPTION

The skid control ECU (brake actuator assembly) inputs the stop light signal and brake operation condition.

When the brake pedal is depressed and the stop light switch signal is not input, this DTC is output.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area
P057111	Brake Switch "A" Circuit Short to Ground	Either of the following is detected: When the +BS terminal voltage is 9.5 V or higher and the brake pedal load sensing switch is ON, the stop light switch signal is input continuously for 2 seconds or more with the master cylinder pressure at 2 MPa (20.4 kgf/cm2) or higher and the deceleration calculated from the vehicle speed at 0.2 G or higher. After a master cylinder pressure of more than 1.764 MPa (18.0 kgf/cm2) is detected for 5 seconds or more continuously at a vehicle speed below 3 km/h (2 mph) with the stop light switch assembly off, the master cylinder pressure exceeds 1.764 MPa (18.0 kgf/cm2) for 1 second or more continuously while and the stop light switch assembly signal is not received when the vehicle decelerates from over 35 km/h (22 mph) to 3 km/h (2 mph).	Stop light switch assembly Wire harness and connector Brake pedal load sensing switch (brake pedal support assembly) Skid control ECU (brake actuator assembly)

DTC Detection Conditions: P057111

		Vehicle Condition
		Pattern 1	Pattern 2
Diagnosis Condition	+BS terminal voltage 9.5 V or higher	○	-
Malfunction Status	When the brake pedal load sensing switch is ON, the stop light switch signal is input continuously for 2 seconds or more with the master cylinder pressure at 2 MPa (20.4 kgf/cm2) or higher and the deceleration calculated from the vehicle speed at 0.2 G or higher.	○	-
	After a master cylinder pressure of more than 1.764 MPa (18.0 kgf/cm2) is detected for 5 seconds or more continuously at a vehicle speed below 3 km/h (2 mph) with the stop light switch assembly off, the master cylinder pressure exceeds 1.764 MPa (18.0 kgf/cm2) for 1 second or more continuously while and the stop light switch assembly signal is not received when the vehicle decelerates from over 35 km/h (22 mph) to 3 km/h (2 mph)	-	○
Detection Time		2 seconds or more	-
Number of Trips		1 trip	1 trip

HINT:

DTC will be output when conditions for either of the patterns in the table above are met.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

PROCEDURE

1.	CHECK BRAKE PEDAL HEIGHT AND STOP LIGHT SWITCH ASSEMBLY INSTALLATION

(a) Check the brake pedal height and stop light switch assembly installation.

Click here

OK:

The brake pedal height and stop light switch assembly installation are normal.

HINT:

If the on/off status of the stop light switch assembly and the pressure increase information from the master cylinder pressure sensor do not match due to an improperly installed brake pedal or stop light switch assembly, this DTC may be stored. Therefore, be sure to check the installation condition of the pedal and stop light switch assembly before inspecting the input signals and other related parts.

NG

ADJUST BRAKE PEDAL HEIGHT OR STOP LIGHT SWITCH ASSEMBLY INSTALLATION

OK

2.	CHECK STOP LIGHT OPERATION

(a) Check that the stop lights come on when the brake pedal is depressed, and go off when the brake pedal is released.

OK:

Condition	Illumination Condition
Brake pedal depressed.	On
Brake pedal released.	Off

NG

GO TO STEP 11

OK

3.	READ VALUE USING TECHSTREAM (STOP LIGHT SW)

(a) Connect the Techstream to the DLC3.

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

(c) Enter the following menus: Chassis / Brake/EPB / Data List.

Chassis > Brake/EPB > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Stop Light SW	Stop light switch assembly (STP terminal input)	OFF / ON	OFF: Brake pedal released ON: Brake pedal depressed	HINT: The brake pedal state is determined using the voltage at terminal STP
Brake Pedal Load Sensing SW	Brake pedal load sensing switch	OFF / ON	OFF: Brake pedal released ON: Brake pedal depressed	-

Chassis > Brake/EPB > Data List

Tester Display
Stop Light SW
Brake Pedal Load Sensing SW

(d) Check that the stop light switch display and brake pedal load sensing switch display observed on the Techstream change according to brake pedal operation.

OK:

The Techstream displays OFF / ON according to brake pedal operation.

(e) Slowly depress the brake pedal, and check when the stop light switch assembly and brake pedal load sensing switch turn on.

OK:

First the stop light switch assembly should turn on, and then the brake pedal load sensing switch should turn on.

Result	Proceed to
OK	A
NG (The stop light switch assembly does not turn on.)	B
NG (Turning on of the brake pedal load sensing switch is not confirmed.)	C
NG (The brake pedal load sensing switch turns on first.)	D

B

GO TO STEP 6

C

GO TO STEP 10

D

REPLACE BRAKE PEDAL SUPPORT ASSEMBLY

A

4.

CLEAR DTC

(a) Operate the Techstream to clear the codes. Enter the following menus: Chassis / Brake/EPB / Trouble Codes.

Chassis > Brake/EPB > Clear DTCs

(b) Press the DTC clear button.

(c) Turn the engine switch off.

NEXT

5.	RECONFIRM DTC

(a) Start the engine.

(b) Perform a road test.

(c) Read the DTCs following the prompts on the Techstream. Enter the following menus: Chassis / Brake/EPB / Trouble Codes.

Chassis > Brake/EPB > Trouble Codes

(d) Check if the same DTC is output.

Result	Proceed to
DTC P057111 is not output.	A
DTC P057111 is output.	B

A

USE SIMULATION METHOD TO CHECK

B

REPLACE BRAKE ACTUATOR ASSEMBLY

6.	CHECK HARNESS AND CONNECTOR (STP TERMINAL)

(a) Turn the engine switch off.

*a Front view of wire harness connector (to Skid Control ECU (Brake Actuator Assembly))

(b) Make sure that there is no looseness at the locking part and the connecting part of the connectors.

OK:

The connector is securely connected.

(c) Disconnect the A41 skid control ECU (brake actuator assembly) connector.

(d) Check both the connector case and the terminals for deformation and corrosion.

OK:

No deformation or corrosion.

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
A41-11 (STP) - Body ground	Stop light switch assembly on (Brake pedal depressed)	8 to 14 V
A41-11 (STP) - Body ground	Stop light switch assembly off (Brake pedal released)	Below 1.5 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

7.

CLEAR DTC

(a) Reconnect the A41 skid control ECU (brake actuator assembly) connector.

(b) Operate the Techstream to clear the codes. Enter the following menus: Chassis / Brake/EPB / Trouble Codes.

Chassis > Brake/EPB > Clear DTCs

(c) Press the DTC clear button.

(d) Turn the engine switch off.

NEXT

8.	RECONFIRM DTC

(a) Start the engine.

(b) Perform a road test.

(c) Read the DTCs following the prompts on the Techstream. Enter the following menus: Chassis / Brake/EPB / Trouble Codes.

Chassis > Brake/EPB > Trouble Codes

(d) Check if the same DTC is output.

Result	Proceed to
DTC P057111 is not output.	A
DTC P057111 is output.	B

B

REPLACE BRAKE ACTUATOR ASSEMBLY

A

9.	INSPECT BRAKE PEDAL SUPPORT ASSEMBLY

(a) Turn the engine switch off.

*a Component without harness connected (Brake Pedal Load Sensing Switch (Brake Pedal Support Assembly))

(b) Make sure that there is no looseness at the locking part and the connecting part of the connectors.

OK:

The connector is securely connected.

(c) Disconnect the A51 brake pedal load sensing switch (brake pedal support assembly) connector.

(d) Check both the connector case and the terminals for deformation and corrosion.

OK:

No deformation or corrosion.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
2 (FSW+) - 1 (FSW-)	Brake pedal load sensing switch off (Brake pedal depressed)	950 to 1050 Ω
2 (FSW+) - 1 (FSW-)	Brake pedal load sensing switch on (Brake pedal released)	203 to 223 Ω

OK

GO TO STEP 10

NG

REPLACE BRAKE PEDAL SUPPORT ASSEMBLY

10.	CHECK HARNESS AND CONNECTOR (BRAKE PEDAL SUPPORT ASSEMBLY - BRAKE ACTUATOR ASSEMBLY)

(a) Make sure that there is no looseness at the locking part and the connecting part of the connectors.

OK:

The connector is securely connected.

(b) Disconnect the A41 skid control ECU (brake actuator assembly) connector.

(c) Disconnect the A51 brake pedal load sensing switch (brake pedal support assembly) connector.

(d) Check both the connector case and the terminals for deformation and corrosion.

OK:

No deformation or corrosion.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
A51-2 (FSW+) - A41-28 (FSW+)	Always	Below 1 Ω
A51-2 (FSW+) or A41-28 (FSW+) - Body ground	Always	10 kΩ or higher
A51-1 (FSW-) - Body ground	1 minute or more after disconnecting the cable from the negative (-) battery terminal	Below 1 Ω

OK

REPLACE BRAKE ACTUATOR ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

11.	INSPECT STOP LIGHT SWITCH ASSEMBLY

(a) Inspect the stop light switch assembly.

Click here

OK:

The stop light switch assembly is normal.

NG

REPLACE STOP LIGHT SWITCH ASSEMBLY

OK

12.	CHECK HARNESS AND CONNECTOR (STP TERMINAL)

(a) Turn the engine switch off.

*a Front view of wire harness connector (to Skid Control ECU (Brake Actuator Assembly))

(b) Make sure that there is no looseness at the locking part and the connecting part of the connectors.

OK:

The connector is securely connected.

(c) Disconnect the A41 skid control ECU (brake actuator assembly) connector.

(d) Check both the connector case and the terminals for deformation and corrosion.

OK:

No deformation or corrosion.

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
A41-11 (STP) - Body ground	Stop light switch assembly on (Brake pedal depressed)	8 to 14 V
A41-11 (STP) - Body ground	Stop light switch assembly off (Brake pedal released)	Below 1.5 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

13.

CLEAR DTC

(a) Reconnect the A41 skid control ECU (brake actuator assembly) connector.

(b) Connect the Techstream to the DLC3.

(c) Turn the engine switch on (IG).

(d) Operate the Techstream to clear the codes. Enter the following menus: Chassis / Brake/EPB / Trouble Codes.

Chassis > Brake/EPB > Clear DTCs

(e) Press the DTC clear button.

(f) Turn the engine switch off.

NEXT

14.	RECONFIRM DTC

(a) Start the engine.

(b) Perform a road test.

(c) Read the DTCs following the prompts on the Techstream. Enter the following menus: Chassis / Brake/EPB / Trouble Codes.

Chassis > Brake/EPB > Trouble Codes

(d) Check if the same DTC is output.

Result	Proceed to
DTC P057111 is not output.	A
DTC P057111 is output.	B

A

USE SIMULATION METHOD TO CHECK

B

REPLACE BRAKE ACTUATOR ASSEMBLY