Toyota CH-R Service Manual: Master Cylinder Pressure Sensor Malfunction (C1246)

DESCRIPTION

The master cylinder pressure sensor is connected to the skid control ECU in the brake actuator assembly.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area
C1246	Master Cylinder Pressure Sensor Malfunction	Any of the following is detected: The voltage of the sensor signal is out of range (below 0.129 V, above 3.29 V). An abnormality is detected in the skid control ECU internal sensor test. The sensor signal offset value is out of range.	Stop light switch circuit Master cylinder pressure sensor circuit Master cylinder pressure sensor (brake actuator assembly)

DTC Detection Conditions:

		Vehicle Condition
		Pattern 1	Pattern 2	Pattern 3
Diagnosis Condition	-	-	-	-
Malfunction Status	The voltage of the sensor signal is out of range (below 0.129 V, above 3.29 V).	○	-	-
	An abnormality is detected in the skid control ECU internal sensor test.	-	○	-
	The sensor signal offset value is out of range.	-	-	○
Detection Time		-	-	-
Number of Trips		1 trip	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

NOTICE:

When replacing the skid control ECU (brake actuator assembly), perform system variant learning.

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PROCEDURE

1.	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

INSPECT LIGHTING SYSTEM (STOP LIGHT CIRCUIT)

OK

2.	READ VALUE USING TECHSTREAM (MASTER CYLINDER PRESSURE SENSOR)

(a) Connect the Techstream to the DLC3.

(b) Start the engine.

(c) Select the Data List using the Techstream.

Click here

Chassis > ABS/VSC/TRAC/EPB > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Master Cylinder Sensor	Master cylinder pressure sensor reading	Min.: 0.00 V, Max.: 5.00 V	When brake pedal released: 0.2 to 0.4 V	Reading increases when brake pedal is depressed

Chassis > ABS/VSC/TRAC/EPB > Data List

Tester Display
Master Cylinder Sensor

(d) Check that the brake fluid pressure value of the master cylinder pressure sensor observed on the Techstream changes when the brake pedal is depressed.

OK:

When the pedal is depressed, the voltage displayed on the Techstream increases.

NG

REPLACE BRAKE ACTUATOR ASSEMBLY

OK

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

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Select the Data List using the Techstream.

Click here

Chassis > ABS/VSC/TRAC/EPB > Data List

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

Chassis > ABS/VSC/TRAC/EPB > Data List

Tester Display
Stop Light SW

(d) Check that the stop light switch 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 5

OK

4.	RECONFIRM DTC

(a) Turn the ignition switch off.

(b) Clear the DTCs.

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Chassis > ABS/VSC/TRAC/EPB > Clear DTCs

(c) Turn the ignition switch off.

(d) Start the engine.

(e) Drive the vehicle and depress the brake pedal several times to test the stop light circuit.

(f) Check if the same DTC is output.

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Chassis > ABS/VSC/TRAC/EPB > Trouble Codes

Result	Proceed to
DTC C1246 is not output.	A
DTC C1246 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 before replacing parts.

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A

USE SIMULATION METHOD TO CHECK

B

REPLACE BRAKE ACTUATOR ASSEMBLY

5.	CHECK HARNESS AND CONNECTOR (STP TERMINAL)

(a) Turn the ignition 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 connector.

(c) Disconnect the A42 skid control ECU (brake actuator assembly) connector.

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
A42-44 (STP2) - Body ground	Stop light switch ON (Brake pedal depressed)	11 to 14 V*
A42-44 (STP2) - Body ground	Stop light switch OFF (Brake pedal released)	Below 1.5 V

HINT:

*: The standard voltage value varies depending on the +BS terminal voltage value. The standard voltage is 85% of the +BS terminal voltage.

HINT:

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

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OK

REPLACE BRAKE ACTUATOR ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT)