Toyota Avalon (XX50): Brake Warning Light does not Come ON. Brake Warning Light Remains ON. Open Circuit in ABS Motor Relay Circuit (C146C)

Toyota Avalon (XX50) 2019-2022 Service & Repair Manual / Brake / Brake Control / Dynamic Control Systems / Electronically Controlled Brake System(for Gasoline Model) / Brake Warning Light does not Come ON. Brake Warning Light Remains ON. Open Circuit in ABS Motor Relay Circuit (C146C)

Brake Warning Light does not Come ON

DESCRIPTION

The skid control ECU (brake actuator assembly) is connected to the combination meter assembly via CAN communication.

CAUTION / NOTICE / HINT

NOTICE:

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

PROCEDURE

1.	CHECK CAN COMMUNICATION SYSTEM

(a) Check if CAN communication system DTCs are output.

Click here

Result	Proceed to
DTCs are not output	A
DTCs are output	B

INSPECT CAN COMMUNICATION SYSTEM

2.	PERFORM ACTIVE TEST USING TECHSTREAM (BRAKE WARNING LIGHT)

(a) Enter the following menus: Chassis / ABS/VSC/TRAC/EPB / Active Test.

Chassis > ABS/VSC/TRAC/EPB > Active Test

Tester Display	Measurement Item	Control Range	Diagnostic Note
Brake Warning Light	Brake system warning light (red indicator)	Warning light OFF/ON	Observe combination meter assembly

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

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Brake Warning Light	Brake system warning light (red indicator)	ON or OFF	ON: Warning light on OFF: Warning light off	-

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Brake Warning Light

Brake system warning light (red indicator)

ON or OFF

ON: Warning light on

OFF: Warning light off

Chassis > ABS/VSC/TRAC/EPB > Active Test

Active Test Display
Brake Warning Light

Data List Display
Brake Warning Light

(b) Check the operating condition of the brake system warning light (red indicator) when operating it using the Techstream.

Result	Proceed to
Brake warning light in the Data List does not change using the Active Test	A
Brake warning light in the Data List turns ON/OFF using the Active Test	B

REPLACE BRAKE ACTUATOR ASSEMBLY

3.	INSPECT COMBINATION METER ASSEMBLY

(a) Enter the following menus: Body Electrical / Combination Meter / Active Test.

(b) Perform the Active Test of the combination meter assembly using the Techstream.

Body Electrical > Combination Meter > Active Test

Tester Display
Brake Warning

OK:

The brake system warning light (red indicator) turns on or off in accordance with Techstream operation.

REPLACE BRAKE ACTUATOR ASSEMBLY

INSPECT METER / GAUGE SYSTEM

Brake Warning Light Remains ON

DESCRIPTION

The skid control ECU (brake actuator assembly) is connected to the combination meter assembly via CAN communication.

If any of the following is detected, the brake system warning light (red indicator) remains on:

The skid control ECU (brake actuator assembly) connector is disconnected from the skid control ECU (brake actuator assembly).
The brake fluid level is insufficient.
The vacuum inside the brake booster decreases.
EBD operation is not possible.

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.
Before performing this procedure, depress the brake pedal and confirm that the stop lights illuminate.

PROCEDURE

1.	CHECK CAN COMMUNICATION SYSTEM

(a) Check if CAN communication system DTCs are output.

Click here

Result	Proceed to
DTCs are not output	A
DTCs are output	B

INSPECT CAN COMMUNICATION SYSTEM

2.	CHECK IF BRAKE ACTUATOR ASSEMBLY CONNECTOR IS SECURELY CONNECTED

(a) Check if the skid control ECU (brake actuator assembly) connector is securely connected.

OK:

The connector is securely connected.

CONNECT CONNECTOR TO BRAKE ACTUATOR ASSEMBLY CORRECTLY

3.	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

4.	CHECK HARNESS AND CONNECTOR (POWER SOURCE 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
A28-30 (+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)

5.	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)

6.	INSPECT BRAKE MASTER CYLINDER RESERVOIR ASSEMBLY

(a) Turn the engine switch off.

*a	Component without harness connected (Brake Fluid Level Warning Switch (Brake Master Cylinder Reservoir Assembly))

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

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

OK:

The connector is securely connected.

(e) Disconnect the A1 brake fluid level warning switch (brake master cylinder reservoir assembly) connector.

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

OK:

No deformation or corrosion.

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

HINT:

A float is located inside the reservoir. Its position changes according to the brake fluid level.

Standard Resistance:

Tester Connection	Condition	Specified Condition
1 (+) - 2 (E)	Switch off (float up)	1.9 to 2.1 kΩ
1 (+) - 2 (E)	Switch on (float down)	Below 1 Ω

(h) If there is no problem after finishing the above check, adjust the brake fluid level to the MAX level.

REPLACE BRAKE MASTER CYLINDER RESERVOIR ASSEMBLY

7.	CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - BRAKE MASTER CYLINDER RESERVOIR 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 G16 combination meter assembly connector.

OK:

No deformation or corrosion.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
G16-12 (SW) - A1-1 (+)	Always	Below 1 Ω
G16-12 (SW) or A1-1 (+) - Body ground	Always	10 kΩ or higher
A1-2 (E) - Body ground	Always	Below 1 Ω

REPAIR OR REPLACE HARNESS OR CONNECTOR

8.	INSPECT VACUUM WARNING SWITCH ASSEMBLY

(a) Reconnect the A1 brake fluid level warning switch (brake master cylinder reservoir assembly) connector.

(b) Reconnect the G16 combination meter assembly connector.

Click here

OK:

The vacuum warning switch assembly is normal.

REPLACE VACUUM WARNING SWITCH ASSEMBLY

9.	CHECK HARNESS AND CONNECTOR (COMBINATION METER ASSEMBLY - VACUUM WARNING SWITCH 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 A2 vacuum warning switch assembly connector.

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

OK:

No deformation or corrosion.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
G16-7 (VCM) - A2-2 (+)	Always	Below 1 Ω
G16-7 (VCM) or A2-2 (+) - Body ground	Always	10 kΩ or higher
A2-1 (E) - Body ground	Always	Below 1 Ω

REPAIR OR REPLACE HARNESS OR CONNECTOR

10.	READ VALUE USING TECHSTREAM (BRAKE WARNING LIGHT)

(a) Reconnect the A2 vacuum warning switch assembly connector.

(b) Reconnect the G16 combination meter assembly connector.

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

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Brake Warning Light

Brake system warning light (red indicator)

ON or OFF

ON: Warning light on

OFF: Warning light off

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

Tester Display
Brake Warning Light

(d) Check the Techstream display condition of the brake system warning light (red indicator).

Result	Proceed to
The value of Brake Warning Light is ON	A
The value of Brake Warning Light is OFF	B

REPLACE BRAKE ACTUATOR ASSEMBLY

INSPECT METER / GAUGE SYSTEM

Open Circuit in ABS Motor Relay Circuit (C146C)

DESCRIPTION

The ABS motor relay supplies power to the pump motor. While the ABS is activated, the skid control ECU (brake actuator assembly) turns the ABS motor relay on to operate the pump motor.

If the voltage supplied to the ABS motor relay (+BM) is too low due to low voltage from the battery or alternator, this DTC may be stored.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

C146C

Open Circuit in ABS Motor Relay Circuit

Any of the following is detected:

When the ABS motor relay is actuated, voltage is not supplied to the pump motor.
When the ABS motor relay is not actuated, voltage in the pump motor is high.
The skid control ECU (brake actuator assembly) judges that pump motor operation is abnormal.

ABS NO. 1 fuse
ABS motor relay circuit
ABS motor relay (brake actuator assembly)

DTC Detection Conditions: C146C

		Vehicle Condition
		Pattern 1	Pattern 2	Pattern 3
Diagnosis Condition	The ABS motor relay is actuated.	○	-	-
Diagnosis Condition	The ABS motor relay is not actuated.	-	○	-
Malfunction Status	Voltage is not supplied to the pump motor.	○	-	-
	Voltage in the pump motor is high.	-	○	-
	The skid control ECU (brake actuator assembly) judges that pump motor operation is abnormal.	-	-	○
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 and acceleration sensor zero point calibration.
Click here
Inspect the fuses for circuits related to this system before performing the following procedure.

HINT:

When C1241 and/or C1417 is output together with C146C, inspect and repair the trouble areas indicated by C1241 and/or C1417 first.

for C1241: Click here

for C1417: Click here

PROCEDURE

1.	PERFORM ACTIVE TEST USING TECHSTREAM (ABS MOTOR RELAY)

(a) Connect the Techstream to the DLC3.

(b) Start the engine.

Chassis > ABS/VSC/TRAC/EPB > Active Test

Tester Display	Measurement Item	Control Range	Diagnostic Note
Motor Relay	ABS motor relay	Relay OFF/ON	Operating sound of motor can be heard

Chassis > ABS/VSC/TRAC/EPB > Active Test

Tester Display
Motor Relay

(d) Check the operating sound of the pump motor when operating it using the Techstream.

Result	Proceed to
Operating sound is heard	A
Operating sound is not heard	B

GO TO STEP 3

2.	RECONFIRM DTC

HINT:

This DTC is stored when a problem is identified in the skid control ECU (brake actuator assembly).

The ABS motor relay is in the skid control ECU (brake actuator assembly).

Therefore, ABS motor relay inspection and ABS motor relay unit inspection cannot be performed. Be sure to check if the DTC is output again before replacing the skid control ECU (brake actuator assembly).

(a) Clear the DTCs.

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

(b) Turn the engine switch off.

(d) Drive the vehicle at a speed of 40 km/h (25 mph) or more for 30 seconds or more.

(e) Check if the same DTC is output.

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

Result	Proceed to
C146C is not output	A
C146C is output	B

HINT:

If a speed signal of 40 km/h (25 mph) or more is received by the skid control ECU (brake actuator assembly) with the engine switch on (IG), the skid control ECU (brake actuator assembly) performs self diagnosis of the motor circuit.
If the normal system code is output (no DTCs are output), slightly jiggle the connectors, wire harness, and fuses of the skid control ECU (brake actuator assembly).
If any DTCs are output while jiggling a connector or wire harness of the skid control ECU (brake actuator assembly), inspect and repair the connector or wire harness.
If no DTCs were output when reconfirming DTCs, checking for intermittent problems is necessary because it is suspected that the original DTCs were stored due to the poor connection of a connector terminal.

USE SIMULATION METHOD TO CHECK

REPLACE BRAKE ACTUATOR ASSEMBLY

3.	CHECK HARNESS AND CONNECTOR (+BM 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
A28-1 (+BM) - Body ground	Always	11 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR (+BM CIRCUIT)

4.	CHECK HARNESS AND CONNECTOR (GND2 TERMINAL)

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
A28-14 (GND2) - Body ground	Always	Below 1 Ω

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

REPLACE BRAKE ACTUATOR ASSEMBLY

REPAIR OR REPLACE HARNESS OR CONNECTOR (GND2 CIRCUIT)

Brake Actuator Operation Sound is Loud during Initial Check. Brake Hold Operated Indicator Light Circuit. Brake Hold Standby Indicator Light Circuit

Open Circuit in ABS Solenoid Relay Circuit (C146E). Air Bag Circuit (C147D). Engine Control System Malfunction (C1201)

See More:

Toyota Avalon (XX50) 2019-2022 Service & Repair Manual > Can Communication System(for Gasoline Model): Open in Bus 4 Main Bus Line. Open in Bus 5 Main Bus Line. Open in One Side of Bus 1 Branch Line
Open in Bus 4 Main Bus Line DESCRIPTION There may be an open circuit in one of the CAN main bus lines when the resistance between terminals 22 (CA2H) and 7 (CA2L) of the central gateway ECU (network gateway ECU) is 70 Ω or higher. Symptom Trouble Area Resistance between terminals 22 (CA2H) and 7 (C ...