Lexus NX: Stop Light Relay Malfunction (C1380)

DESCRIPTION

Upon receiving the hill-start assist control, dynamic radar cruise control, brake hold control or trailer sway control operating signal from the skid control ECU (brake booster with master cylinder assembly), the relay contact turns on and the stop lights come on.

DTC No.	Detection Item	INF Code	DTC Detection Condition	Trouble Area	Note
C1380	Stop Light Relay Malfunction	761 762	INF Code: 761 When the voltage at terminal IG1 is 9.5 V or more, stop light drive output (STPO) is ON and STP2 is OFF for 2 seconds or more. INF Code: 762 When the voltage at terminal IG1 is 9.5 V or more, stop light drive output (STPO) is OFF and the input signals for STP and STP2 differ for 5 seconds or more.	Stop light switch assembly circuit Stop light control ECU assembly circuit Stop light control ECU assembly Skid control ECU (Brake booster with master cylinder assembly)	-

WIRING DIAGRAM

CAUTION / NOTICE / HINT

HINT:

When C1249 is output together with C1380, inspect and repair the trouble areas indicated by C1249 first.

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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

INSPECT LIGHTING SYSTEM

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 condition 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 8

OK

3.	PERFORM ACTIVE TEST USING TECHSTREAM (STOP LIGHT CONTROL ECU ASSEMBLY)

(a) Select the Active Test on the Techstream.

Click here

Chassis > ABS/VSC/TRAC > Active Test

Tester Display	Measurement Item	Control Range	Diagnostic Note
Stop Light Relay	Stop light control ECU assembly (stop light control relay)	ECU (Relay) ON/OFF	Stop lights come on

Chassis > ABS/VSC/TRAC > Active Test

Tester Display
Stop Light Relay

(b) Perform the Active Test of the stop light control ECU assembly using the Techstream.

(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 Relay Output	Stop light control ECU assembly (stop light control relay) output	ON or OFF	ON: ECU (Relay) output on OFF: ECU (Relay) output off	-

Chassis > ABS/VSC/TRAC > Data List

Tester Display
Stop Light Relay Output

(d) Check for stop light control ECU assembly operation using the Data List and stop light operation by performing the Active Test.

Result	Proceed to
Data List content and stop light operation are normal.	A
Data List content and stop light operation are abnormal or Data List content is normal but stop lights do not turn on or off.	B

B

GO TO STEP 6

A

4.	CHECK HARNESS AND CONNECTOR (STP2 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
A57-6 (STP2) - Body ground	Stop light switch assembly on (Brake pedal depressed)	11 to 14 V
A57-6 (STP2) - Body ground	Stop light switch assembly off (Brake pedal released)	Below 1.5 V

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (STP2 CIRCUIT)

OK

5.	RECONFIRM DTC

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

(b) Clear the DTCs.

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Chassis > ABS/VSC/TRAC > Clear DTCs

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

(d) Perform a road test.

(e) Check if the same DTC is output.

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Chassis > ABS/VSC/TRAC > Trouble Codes

Result	Proceed to
DTC C1380 is not output.	A
DTC C1380 is output.	B

A

USE SIMULATION METHOD TO CHECK

B

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

6.	INSPECT STOP LIGHT CONTROL ECU ASSEMBLY

(a) Turn the power switch off.

(b) Check the stop light control ECU assembly.

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OK:

The stop light control ECU assembly is normal.

NG

REPLACE STOP LIGHT CONTROL ECU ASSEMBLY

OK

7.	CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - STOP LIGHT CONTROL ECU ASSEMBLY)

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

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

(c) Disconnect the A3 stop light control ECU assembly connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
A57-3 (STPO) -A3-9 (ACC)	Always	Below 1 Ω
A57-3 (STPO) or A3-9 (ACC) - Body ground	Always	10 kΩ or higher

OK

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

8.	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

OK

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT)

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