Toyota Avalon (XX50): Low or High Power Supply Voltage (C1241). Master Cylinder Pressure Sensor (C1246). Open Circuit in Stop Light Switch Circuit (C1249)

Toyota Avalon (XX50) 2019-2022 Service & Repair Manual / Brake / Brake Control / Dynamic Control Systems / Electronically Controlled Brake System(for Gasoline Model) / Low or High Power Supply Voltage (C1241). Master Cylinder Pressure Sensor (C1246). Open Circuit in Stop Light Switch Circuit (C1249)

Low or High Power Supply Voltage (C1241)

DESCRIPTION

If a malfunction is detected in the power supply circuit, the skid control ECU (brake actuator assembly) stores this DTC and the fail-safe function prohibits ABS operation. This DTC is stored when the +BS terminal voltage meets one of the DTC detection conditions due to a malfunction in the power supply or charging circuit such as the battery or alternator circuit, etc. The DTC is cleared when the +BS terminal voltage returns to normal.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area
C1241	Low or High Power Supply Voltage	Any of the following is detected: The vehicle speed is 6 km/h (4 mph) or more and the +BS terminal voltage (soft low voltage) is less than 9.6 V for 1 second or more. The vehicle speed is 6 km/h (4 mph) or more and the +BS terminal voltage (hard low voltage) is less than 6.9 V for 1 second or more. The vehicle speed is 15 km/h (9 mph) or more, the +BS terminal voltage is 9.6 V or more, the skid control ECU (brake actuator assembly) turns on more than one valve at the same time within a short period of time and the valve relay supply voltage drop exceeds the threshold.* The +BS terminal voltage is less than 6.7 V and the skid control ECU (brake actuator assembly) judges that power supply voltage is abnormal for 0.06 seconds or more.	ABS NO. 2 fuse Battery Charging system Power source circuit Ground circuit Internal power supply circuit of the skid control ECU (brake actuator assembly)

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

C1241

Low or High Power Supply Voltage

Any of the following is detected:

The vehicle speed is 6 km/h (4 mph) or more and the +BS terminal voltage (soft low voltage) is less than 9.6 V for 1 second or more.
The vehicle speed is 6 km/h (4 mph) or more and the +BS terminal voltage (hard low voltage) is less than 6.9 V for 1 second or more.
The vehicle speed is 15 km/h (9 mph) or more, the +BS terminal voltage is 9.6 V or more, the skid control ECU (brake actuator assembly) turns on more than one valve at the same time within a short period of time and the valve relay supply voltage drop exceeds the threshold.*
The +BS terminal voltage is less than 6.7 V and the skid control ECU (brake actuator assembly) judges that power supply voltage is abnormal for 0.06 seconds or more.

ABS NO. 2 fuse
Battery
Charging system
Power source circuit
Ground circuit
Internal power supply circuit of the skid control ECU (brake actuator assembly)

*: The skid control ECU (brake actuator assembly) monitors the resistance of the power source line at the +BS terminal. A malfunction is detected when an abnormality occurs in the +BS terminal wire harness or its connection and the skid control ECU (brake actuator assembly) determines that the wiring resistance at the +BS terminal exceeds the standard resistance.

DTC Detection Conditions: C1241

		Vehicle Condition
		Pattern 1	Pattern 2	Pattern 3	Pattern 4
Diagnosis Condition	The vehicle speed is 6 km/h (4 mph) or more.	○	○	-	-
	The vehicle speed is 15 km/h (9 mph) or more and the +BS terminal voltage is 9.6 V or more.	-	-	○	-
	The +BS terminal voltage is less than 6.7 V.	-	-	-	○
Malfunction Status	The +BS terminal voltage (soft low voltage) is less than 9.6 V.	○	-	-	-
	The +BS terminal voltage (hard low voltage) is less than 6.9 V.	-	○	-	-
	The skid control ECU (brake actuator assembly) turns on more than one valve at the same time within a short period of time and the valve relay supply voltage drop exceeds the threshold.*	-	-	○	-
	The skid control ECU (brake actuator assembly) judges that power supply voltage is abnormal.	-	-	-	○
Detection Time		1 second or more	1 second or more	-	0.06 seconds or more
Number of Trips		1 trip	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 and acceleration sensor zero point calibration.
Click here
Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

1.	CHECK BATTERY

(a) Check the battery voltage.

Standard Voltage:

Tester Connection	Condition	Specified Condition
Positive (+) terminal - Negative (-) terminal	Engine switch off	11 to 14 V

CHECK OR REPLACE CHARGING SYSTEM COMPONENT OR BATTERY

2.	CHECK HARNESS AND CONNECTOR (POWER SOURCE TERMINAL)

(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.

*a	Front view of wire harness connector (to Skid Control ECU (Brake Actuator Assembly))

(b) Disconnect the A28 skid control ECU (brake actuator assembly) connector.

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
A28-30 (+BS) - Body ground	Always	11 to 14 V
A28-36 (IG1) - Body ground	Engine switch on (IG)	11 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

3.	CHECK HARNESS AND CONNECTOR (GND1 TERMINAL)

(a) Turn the engine switch off.

*a	Front view of wire harness connector (to Skid Control ECU (Brake Actuator Assembly))

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
A28-46 (GND1) - Body ground	Always	Below 1 Ω

REPAIR OR REPLACE HARNESS OR CONNECTOR (GND1 CIRCUIT)

4.	RECONFIRM DTC

(a) Reconnect the A28 skid control ECU (brake actuator assembly) connector.

(b) Clear the DTCs.

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

(d) Start the engine.

(e) Perform a road test.

(f) Check if the same DTC is output.

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

Result	Proceed to
C1241 is not output	A
C1241 is output	B

USE SIMULATION METHOD TO CHECK

REPLACE BRAKE ACTUATOR ASSEMBLY

Master Cylinder Pressure Sensor (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	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 assembly circuit Master cylinder pressure sensor circuit Master cylinder pressure sensor (brake actuator assembly)

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

C1246

Master Cylinder Pressure Sensor

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 assembly circuit
Master cylinder pressure sensor circuit
Master cylinder pressure sensor (brake actuator assembly)

DTC Detection Conditions: C1246

		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

Refer to DTC C1249.

Click here

CAUTION / NOTICE / HINT

NOTICE:

When replacing the skid control ECU (brake actuator assembly), perform system variant learning and acceleration sensor zero point calibration.

Click here

PROCEDURE

1.	READ VALUE USING TECHSTREAM (BS1 VOLTAGE VALUE)

(a) Connect the Techstream to the DLC3.

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

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

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
BS1 Voltage Value	+BS voltage value	Min.: 0.00 V, Max.: 20.00 V	-	Changes in proportion to battery voltage

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

Tester Display
BS1 Voltage Value

(d) Take a note of the +BS voltage value.

HINT:

The noted +BS voltage value is used in a later step.

2.	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

INSPECT LIGHTING SYSTEM (STOP LIGHT CIRCUIT)

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

(a) Connect the Techstream to the DLC3.

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

Chassis > ABS/VSC/TRAC/EPB > 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	-

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/EPB > 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.

GO TO STEP 6

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

(a) Start the engine.

(b) Enter the following menus: Chassis / ABS/VSC/TRAC/EPB / Data List.

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	Brake pedal released: 0.20 to 0.40 V	Reading increases when brake pedal is depressed

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

Tester Display
Master Cylinder Sensor

(c) 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 brake pedal is depressed, the voltage displayed on the Techstream increases.

REPLACE BRAKE ACTUATOR ASSEMBLY

5.	RECONFIRM DTC

(a) Clear the DTCs.

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

(b) Turn the engine switch off.

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

(e) Check if the same DTC is output.

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

Result	Proceed to
C1246 is not output	A
C1246 is output	B

USE SIMULATION METHOD TO CHECK

REPLACE BRAKE ACTUATOR ASSEMBLY

6.	CHECK HARNESS AND CONNECTOR (STP TERMINAL)

(a) Turn the engine 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.

OK:

The connector is securely connected.

(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
A28-42 (STP) - Body ground	Stop light switch assembly on (Brake pedal depressed)	(+BS x 0.85) to 14 V*
A28-42 (STP) - Body ground	Stop light switch assembly off (Brake pedal released)	Below 1.5 V

HINT:

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

REPLACE BRAKE ACTUATOR ASSEMBLY

REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT)

Open Circuit in Stop Light Switch Circuit (C1249)

DESCRIPTION

The skid control ECU (brake actuator assembly) receives stop light switch assembly signals and uses them to determine whether or not the brakes are applied. DTCs may be stored if either of the following occurs:

Stop light switch assembly stuck on malfunction.
The accelerator and brake pedals are depressed simultaneously.*

HINT:

*: The skid control ECU (brake actuator assembly) may store this DTC upon judging that a stuck on malfunction has occurred when the accelerator pedal and brake pedal are depressed simultaneously. However, this does not indicate a malfunction.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area
C1249	Open Circuit in Stop Light Switch Circuit	The vehicle speed is 10 km/h (6 mph) or more, the accelerator pedal is depressed, the master cylinder pressure is 0.5 MPa (5.09 kgf/cm2, 72 psi) or less, and the stop light switch assembly is on for 60 seconds or more.	Wire harness or connector Stop light switch assembly Skid control ECU (brake actuator assembly)

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

When replacing the skid control ECU (brake actuator assembly), perform system variant learning and acceleration sensor zero point calibration.
Click here
Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

1.	READ VALUE USING TECHSTREAM (BS1 VOLTAGE VALUE)

(a) Connect the Techstream to the DLC3.

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

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

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
BS1 Voltage Value	+BS voltage value	Min.: 0.00 V, Max.: 20.00 V	-	Changes in proportion to battery voltage

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

Tester Display
BS1 Voltage Value

(d) Take a note of the +BS voltage value.

HINT:

The noted +BS voltage value is used in a later step.

2.	CHECK ACCELERATOR PEDAL AND BRAKE PEDAL OPERATION

(a) Interview the customer to check if the pedals were depressed simultaneously while driving or braking.

OK:

The pedals were not depressed simultaneously.

HINT:

The skid control ECU (brake actuator assembly) may store this DTC upon judging that a stuck on malfunction has occurred when the accelerator pedal and brake pedal are depressed simultaneously.

If the pedals were depressed simultaneously, clear the DTC because it is not a malfunction.

GO TO STEP 7

3.	INSPECT STOP LIGHT SWITCH ASSEMBLY

(a) Inspect the stop light switch assembly.

Click here

OK:

The stop light switch assembly is normal.

REPLACE STOP LIGHT SWITCH ASSEMBLY

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

(a) Connect the Techstream to the DLC3.

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

Chassis > ABS/VSC/TRAC/EPB > 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/EPB > 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.

GO TO STEP 6

5.	RECONFIRM DTC

(a) Clear the DTCs.

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

(b) Turn the engine switch off.

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

(e) Check if the same DTC is output.

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

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

USE SIMULATION METHOD TO CHECK

REPLACE BRAKE ACTUATOR ASSEMBLY

6.	CHECK HARNESS AND CONNECTOR (STP TERMINAL)

(a) Turn the engine 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.

OK:

The connector is securely connected.

(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
A28-42 (STP) - Body ground	Stop light switch assembly on (Brake pedal depressed)	(+BS x 0.85) to 14 V*
A28-42 (STP) - Body ground	Stop light switch assembly off (Brake pedal released)	Below 1.5 V

HINT:

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

REPLACE BRAKE ACTUATOR ASSEMBLY

REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT)

CLEAR DTC

(a) Clear the DTCs.

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

END

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