BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: ELECTRONICALLY CONTROLLED BRAKE SYSTEM (for HV Model): Abnormal Brake Pedal Response on First Depression; 2019 - 2022 MY Avalon HV [04/2018

Last Modified: 08-21-2023	6.11:8.1.0	Doc ID: RM100000001ANLI
Model Year Start: 2019	Model: Avalon HV	Prod Date Range: [04/2018 - ]
Title: BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: ELECTRONICALLY CONTROLLED BRAKE SYSTEM (for HV Model): Abnormal Brake Pedal Response on First Depression; 2019 - 2022 MY Avalon HV [04/2018 - ]

Abnormal Brake Pedal Response on First Depression

DESCRIPTION

If the vehicle has been stopped without opening or closing the driver door for a long period of time, the electronically controlled brake system will not be ready and sufficient fluid pressure may not be stored in the accumulator. In this case, the brake pedal response may not be the same as usual the first time the brake pedal is depressed. This is not a malfunction.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

After replacing the skid control ECU (brake booster with master cylinder assembly), perform linear solenoid valve offset learning, ABS holding solenoid valve learning, yaw rate and acceleration sensor zero point calibration and system information memorization after performing "Reset Memory".

Click here

PROCEDURE

1.	BRAKE PROBLEM CHECK

(a) Check the conditions at the time the problem occurred.

(1) Whether a warning light illuminated or the buzzer sounded.

(2) The number of times the power switch was turned on (IG) since the latest symptom occurred.

(3) Frequency of the symptom.

CHECK DTC

(a) Clear the DTCs.

Click here

Chassis > ABS/VSC/TRAC > Clear DTCs

(b) Turn the power switch off.

(d) Check the DTCs (electronically controlled brake system) that are output.

Click here

Chassis > ABS/VSC/TRAC > Trouble Codes

Result	Proceed to
DTCs C1391 and C1256 are not output.	A
DTCs C1391 and/or C1256 are output.	B

REPAIR CIRCUITS INDICATED BY OUTPUT DTCS

3.	CHECK VEHICLE

(a) Turn the power switch off.

(b) Depress the brake pedal within 2 minutes of opening the driver door and check the response of the brake pedal.

(c) Release the brake pedal and wait for 2 minutes without depressing the brake pedal, opening or closing the driver door or operating the power switch.

(d) After 2 seconds or more have elapsed, depress the brake pedal and check that the first depression response is different to successive depression responses.

HINT:

Compare the response of the brake pedal when the system is in sleep mode and when the stroke simulator is operating.

Result	Proceed to
The response of the brake pedal does not change.	A
The response of the brake pedal changed.	B

END

4.	INSPECT FRONT DOOR COURTESY LIGHT SWITCH ASSEMBLY LH

(a) Set the interior light door switch to ON and check that the map light assembly illuminates, then set the interior light door switch to DOOR.

(b) Check that the map light assembly illuminates when the driver door is opened.

OK:

The map light assembly illuminates when the driver door is opened.

INSPECT LIGHTING SYSTEM (COURTESY LIGHT SWITCH CIRCUIT)

5.	CHECK HARNESS AND CONNECTOR (CTY 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 Booster with Master Cylinder Assembly))

(b) Disconnect the A35 skid control ECU (brake booster with master cylinder 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
A35-24 (CTY) - Body ground	Driver door open	1.5 V or less
A35-24 (CTY) - Body ground	Driver door closed	11 to 14 V

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

REPAIR OR REPLACE HARNESS OR CONNECTOR (CTY CIRCUIT)