Lexus ES: Open in Stop Switch Circuit (C1425,P0573)

DESCRIPTION

The skid control ECU (brake booster with master cylinder assembly) detects the brake operating conditions through a signal transmitted by the stop light switch assembly.

The skid control ECU incorporates a circuit to detect an open circuit. This DTC is output when an open circuit is detected in the stop light signal input line.

DTC No.	Detection Item	INF Code	DTC Detection Condition	Trouble Area	MIL	Note
C1425	Open in Stop Switch Circuit	231	An open stop light switch circuit continues for 10 seconds or more.	Wire harness or connector Stop light switch assembly Skid control ECU (brake booster with master cylinder assembly) Stop light circuit	Comes on	INF Code 231: SAE Code P0572 Electronically controlled brake system DTC
P0573	Brake Switch "A" Circuit High	-	The stop light switch assembly is stuck 10 times or more.	Wire harness or connector Stop light switch assembly Skid control ECU (brake booster with master cylinder assembly)	Comes on	-

MONITOR DESCRIPTION

When the voltage at terminal STP is outside the range of that when the stop light switch assembly is on or the range of that when the stop light switch assembly is off for a certain amount of time, the skid control ECU (brake booster with master cylinder assembly) judges that there is an open in the stop light switch assembly circuit and illuminates the MIL and stores a DTC.

Also, if the voltage at terminal STP is always within the range of that when the stop light switch assembly is on after the vehicle is driven at a certain speed or more and stopped a specific number of times, the skid control ECU (brake booster with master cylinder assembly) judges that the stop light switch assembly is stuck on and illuminates the MIL and stores a DTC.

MONITOR STRATEGY

Related DTCs	P0572: Stop light switch assembly open circuit P0573: Stop light switch assembly circuit high
Required Sensors/Components(Main)	Stop light switch assembly Speed sensor
Required Sensors/Components(Related)	Skid control ECU (brake booster with master cylinder assembly)
Frequency of Operation	Continuous
Duration	10 seconds: P0572 10 times: P0573
MIL Operation	Immediately
Sequence of Operation	None

TYPICAL ENABLING CONDITIONS

All

Monitor runs whenever the following DTCs are not stored

None

P0572

Both of the following conditions are met	-
Serial communication with high side IC	Valid
IG1 voltage	Higher than 9.54 V

P0573

Serial communication with high side IC

Valid

TYPICAL MALFUNCTION THRESHOLDS

P0572

Stop light switch assembly voltage

Higher than 2.75 V, and less than 4.25 V

P0573

Stop light switch assembly voltage when decelerating vehicle from 30 km/h (19 mph) or more to 3 km/h (2 mph)

4.25 V or more

COMPONENT OPERATING RANGE

P0572

All of the following conditions are met	-
Stop light switch assembly on experience	On
Stop light switch assembly off experience	On
Stop light switch assembly voltage	2.75 V or less, or 4.25 V or more

P0573

Both of the following conditions are met	-
Serial communication with high side IC	Valid
Stop light switch assembly voltage	2.75 V or less

CONFIRMATION DRIVING PATTERN

WIRING DIAGRAM

CAUTION / NOTICE / HINT

PROCEDURE

1.	CHECK STOP LIGHT OPERATION

(a) Check that the stop lights come on when the brake pedal is depressed.

Result	Proceed to
All stop lights illuminate when the brake pedal is depressed and turn off when the brake pedal is released.	A
All stop lights do not illuminate when the brake pedal is depressed.	B
One or more stop lights illuminate when the brake pedal is depressed but remain on when the brake pedal is released.	C

B

GO TO STEP 10

C

GO TO STEP 6

A

2.	READ VALUE USING TECHSTREAM (STOP LIGHT SWITCH ASSEMBLY)

(a) Select the Data List on the Techstream.

Click here

Chassis > ABS/VSC/TRAC > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Stop Light SW	Stop light switch assembly	ON or OFF	ON: Brake pedal depressed OFF: Brake pedal released	-

Chassis > ABS/VSC/TRAC > Data List

Tester Display
Stop Light SW

(b) Check the value of Stop Light SW when the brake pedal is depressed.

Result	Proceed to
The value of Stop Light SW is ON.	A
Other than above.	B

B

GO TO STEP 9

A

3.	STOP LIGHT SWITCH ASSEMBLY OUTPUT CIRCUIT INSPECTION

(a) Turn the power switch off.

*a Component with harness connected (Stop Light Switch Assembly)

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

OK:

The connector is securely connected.

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
A43-1 (OUT) - Body ground	Power switch on (IG) The headlights are on The blower motor switch is in the HI position The rear window defogger is turned on Stop light switch assembly off (Brake pedal released)	1.5 V or less

NG

GO TO STEP 6

OK

4.

CLEAR DTC

(a) Clear the DTCs.

Click here

Chassis > ABS/VSC/TRAC > Clear DTCs

NEXT

5.	RECONFIRM DTC

(a) Turn the power switch off.

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

(c) Perform a road test.

(d) Check if the same DTC is output.

Click here

Chassis > ABS/VSC/TRAC > Trouble Codes

Result	Proceed to
DTCs C1425 and P0573 are not output.	A
DTCs C1425 and/or P0573 are output.	B

A

USE SIMULATION METHOD TO CHECK

B

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

6.	CHECK STOP LIGHT SWITCH ASSEMBLY

(a) Turn the power switch off.

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

OK:

The connector is securely connected.

(c) Disconnect the A43 stop light switch assembly connector.

*a Front view of wire harness connector (to Stop Light Switch Assembly)

(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
A43-1 (OUT) - Body ground	Stop light switch assembly off (Brake pedal released)	1.5 V or less

OK

REPLACE STOP LIGHT SWITCH ASSEMBLY

NG

7.	CHECK BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

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

OK:

The connector is securely connected.

(b) Disconnect the A45 skid control ECU (brake booster with master cylinder assembly) connector.

*a Front view of wire harness connector (to Stop Light Switch Assembly)

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

OK:

No deformation or corrosion.

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
A43-1 (OUT) - Body ground	Stop light switch assembly off (Brake pedal released)	1.5 V or less

OK

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

NG

8.	CHECK FOR SHORT TO +B IN STP CIRCUIT

(a) Check that there is no short to +B in the STP circuit (wire harnesses, connectors and stop lights).

OK:

No short to +B.

OK

USE SIMULATION METHOD TO CHECK

NG

REPAIR OR REPLACE MALFUNCTIONING PART

9.	CHECK HARNESS AND CONNECTOR (STP TERMINAL)

(a) Turn the power switch off.

*a Front view of wire harness connector (to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

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

OK:

The connector is securely connected.

(c) Disconnect the A45 skid control ECU (brake booster with master cylinder 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
A45-12 (STP) - Body ground	Stop light switch assembly on (Brake pedal depressed)	11 to 14 V

OK

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT)

10.	CHECK HARNESS AND CONNECTOR (STOP LIGHT SWITCH ASSEMBLY - STOP LIGHT)

(a) Check that there is no open in the wire harnesses and connectors from terminal OUT of the stop light switch assembly to the stop lights.

OK:

No open.

OK

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT)

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