Lexus NX: Open Circuit in Stop Light Switch Circuit (C1249)

DESCRIPTION

The skid control ECU (brake booster with master cylinder assembly) receives the stop light switch assembly signal and detects the brake pedal operation status.

The skid control ECU (brake booster with master cylinder assembly) has an open detection circuit, which stores this DTC if it detects an open in the stop light input line or ground line of the stop light circuit with the stop light switch assembly off (brake pedal not depressed).

DTC No.	Detection Item	INF Code	DTC Detection Condition	Trouble Area	Note
C1249	Open Circuit in Stop Light Switch Circuit	231	When IG1 terminal voltage is 9.5 V or more, an open stop light switch circuit continues for 10 seconds or more.	Harness or connector Stop light switch assembly Skid control ECU (Brake booster with master cylinder assembly)	-

WIRING DIAGRAM

CAUTION / NOTICE / HINT

PROCEDURE

1.	CHECK STOP LIGHT OPERATION

(a) Check that the all 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 5

OK

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

(a) Connect the Techstream to the DLC3.

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

(c) 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

(d) Check that the stop light switch assembly display observed on the Techstream changes according to brake pedal operation.

OK:

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

NG

GO TO STEP 4

OK

3.	RECONFIRM DTC

(a) Clear the DTCs.

Click here

Chassis > ABS/VSC/TRAC > Clear DTCs

(b) Turn the power switch off.

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

(d) Depress the brake pedal several times to test the stop light circuit.

(e) Check if the same DTC is output.

Click here

Chassis > ABS/VSC/TRAC > Trouble Codes

Result	Proceed to
DTC C1249 is not output.	A
DTC C1249 is output.	B

HINT:

If troubleshooting has been carried out according to Problem Symptoms Table, refer back to the table and proceed to the next step.

Click here

A

USE SIMULATION METHOD TO CHECK

B

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

4.	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.

(c) Disconnect the A57 skid control ECU (brake booster with master cylinder assembly) connector.

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
A57-33 (STP) - Body ground	Stop light switch assembly on (Brake pedal depressed)	11 to 14 V
A57-33 (STP) - Body ground	Stop light switch assembly off (Brake pedal released)	Below 1.5 V

HINT:

If troubleshooting has been carried out according to Problem Symptoms Table, refer back to the table and proceed to the next step.

Click here

OK

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT)

5.	INSPECT STOP LIGHT SWITCH ASSEMBLY

(a) Check the stop light switch assembly.

Click here

OK:

The stop light switch assembly is normal.

NG

REPLACE STOP LIGHT SWITCH ASSEMBLY

OK

6.	CHECK HARNESS AND CONNECTOR (STP TERMINAL)

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

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

(b) Disconnect the A57 skid control ECU (brake booster with master cylinder assembly) connector.

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
A57-33 (STP) - Body ground	Stop light switch assembly on (Brake pedal depressed)	11 to 14 V
A57-33 (STP) - Body ground	Stop light switch assembly off (Brake pedal released)	Below 1.5 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT)

OK

7.	RECONFIRM DTC

(a) Reconnect the A57 skid control ECU (brake booster with master cylinder assembly) connector.

(b) Clear the DTCs.

Click here

Chassis > ABS/VSC/TRAC > Clear DTCs

(c) Turn the power switch off.

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

(e) Depress the brake pedal several times to test the stop light circuit.

(f) Check if the same DTC is output.

Click here

Chassis > ABS/VSC/TRAC > Trouble Codes

Result	Proceed to
DTC C1249 is not output.	A
DTC C1249 is output.	B

A

USE SIMULATION METHOD TO CHECK

B

INSPECT LIGHTING SYSTEM

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