Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Brake Pedal Switch "A" Stuck On (C00409E,C00409F)

DESCRIPTION

The brake pedal load sensing switch signal turns on when the brake pedal is depressed with a force exceeding a predetermined level.

The skid control ECU (brake actuator assembly) uses this circuit to detect if the brake pedal is depressed or not.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area
C00409E	Brake Pedal Switch "A" Stuck On	Either of the following is detected: When the +BS terminal voltage is 9.5 V or higher with the stop light switch signal off, the brake pedal load sensing switch signal on, the master cylinder pressure below 0.7 MPa (71.1 kgf/cm2, 101 psi), and the engine speed 500 rpm or higher, the deceleration is below 0.08 G for 10 seconds or more. When the +BS terminal voltage is 9.5 V or higher, the condition that the brake pedal load sensing switch signal remains on while the vehicle speed increases from 0 km/h (0 mph) to 30 km/h (19 mph) occurs 5 times in succession.	Brake pedal load sensing switch (brake pedal support assembly) Wire harness and connector Skid control ECU (brake actuator assembly)
C00409F	Brake Pedal Switch "A" Stuck Off	Either of the following is detected: When the +BS terminal voltage is from 9.5 to 17.4 V with the stop light switch signal on, the brake pedal load sensing switch signal off, and the master cylinder pressure 6 MPa (61.2 kgf/cm2, 870 psi) or more, the deceleration is 0.4 G or more for 1 second or more. When the +BS terminal voltage is from 9.5 to 17.4 V with the stop light switch signal on, the brake pedal load sensing switch signal off, and the master cylinder pressure exceeding 6 MPa (61.2 kgf/cm2, 870 psi), the vehicle speed is 0 km/h (0 mph) for 5 seconds or more.	Brake pedal load sensing switch (brake pedal support assembly) Wire harness and connector Skid control ECU (brake actuator assembly)

DTC Detection Conditions: C00409E

		Vehicle Condition
		Pattern 1	Pattern 2
Diagnosis Condition	When the +BS terminal voltage is 9.5 V or higher	○	○
Malfunction Status	With the stop light switch signal off, the brake pedal load sensing switch signal on, the master cylinder pressure below 0.7 MPa (71.1 kgf/cm2, 101 psi), and the engine speed 500 rpm or higher, the deceleration is below 0.08 G	○	-
	The condition that the brake pedal load sensing switch signal remains on while the vehicle speed increases from 0 km/h (0 mph) to 30 km/h (19 mph) occurs 5 times in succession	-	○
Detection Time		10 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.

DTC Detection Conditions: C00409F

		Vehicle Condition
		Pattern 1	Pattern 2
Diagnosis Condition	When the +BS terminal voltage is from 9.5 to 17.4 V	○	○
Malfunction Status	With the stop light switch signal on, the brake pedal load sensing switch signal off, and the master cylinder pressure 6 MPa (61.2 kgf/cm2, 870 psi) or more, the deceleration is 0.4 G or more	○	-
	With the stop light switch signal on, the brake pedal load sensing switch signal off, and the master cylinder pressure exceeding 6 MPa (61.2 kgf/cm2, 870 psi), the vehicle speed is 0 km/h (0 mph)	-	○
Detection Time		1 second or more.	5 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

Refer to DTC C004013.

Click here

CAUTION / NOTICE / HINT

NOTICE:

After replacing the skid control ECU (brake actuator assembly), perform "Calibration".

Click here

HINT:

When P057111 and/or P057113 is output together with C00409E and/or C00409F, inspect and repair the trouble areas indicated by P057111 and/or P057113 first.

for P057111: Click here

for P057113: Click here

PROCEDURE

1.	READ VALUE USING TECHSTREAM (STOP LIGHT SW AND BRAKE PEDAL LOAD SENSING SW)

(a) Connect the Techstream to the DLC3.

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

(c) Select the Data List using the Techstream.

Click here

Chassis > Brake/EPB > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Stop Light SW	Stop light switch assembly	OFF / ON	OFF: Brake pedal released ON: Brake pedal depressed	-
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 (Turning on of the brake pedal load sensing switch is not confirmed.)	B
NG (The brake pedal load sensing switch turns on first.)	C

B

GO TO STEP 4

C

GO TO STEP 6

A

2.

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

3.	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 C00409E and C00409F are not output.	A
DTC C00409E and/or C00409F are output.	B

A

USE SIMULATION METHOD TO CHECK

B

REPLACE BRAKE ACTUATOR ASSEMBLY

4.	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

NG

REPLACE BRAKE PEDAL SUPPORT ASSEMBLY

OK

5.	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) 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

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

(a) Turn the engine switch off.

(b) 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.

OK

REPLACE BRAKE PEDAL SUPPORT ASSEMBLY

NG

ADJUST BRAKE PEDAL HEIGHT OR STOP LIGHT SWITCH ASSEMBLY INSTALLATION