BRAKE CONTROL / DYNAMIC CONTROL SYSTEMS: ELECTRONICALLY CONTROLLED BRAKE SYSTEM (for HV Model): C1391; Abnormal Leak in Accumulator; 2019 - 2022 MY Avalon HV [04/2018

Last Modified: 08-21-2023	6.11:8.1.0	Doc ID: RM100000001ANJR
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): C1391; Abnormal Leak in Accumulator; 2019 - 2022 MY Avalon HV [04/2018 - ]

DTC

C1391

Abnormal Leak in Accumulator

DESCRIPTION

This DTC is stored if internal or external brake fluid leaks are detected due to improper sealing in the brake actuator (brake booster with master cylinder assembly) or brake booster pump assembly. Internal leaks are suspected if the pump motor operates frequently without braking.

DTC No.	Detection Item	INF Code	DTC Detection Condition	Trouble Area	MIL	Note
C1391	Abnormal Leak in Accumulator	351	Either of the following is detected: When the brake pedal is not depressed and the pump motor is operating, the accumulator pressure sensor value does not increase a certain number of times. When the brake pedal is not depressed and the pump motor is not operating, the accumulator pressure sensor decrease rate exceeds a certain threshold a certain number of times.	Brake fluid leaks Brake actuator (brake booster with master cylinder assembly) (Malfunctioning internal seal etc.) Brake booster pump assembly (Accumulator internal gas pressure decrease, etc.)	Does not come on	Electronically controlled brake system DTC

DTC Detection Conditions: C1391 INF Code: 351

		Vehicle Condition
		Pattern 1	Pattern 2
Diagnosis Condition	Brake pedal not depressed and pump motor operating.	○	-
Diagnosis Condition	Brake pedal not depressed and pump motor not operating.	-	○
Malfunction Status	The accumulator pressure sensor value does not increase a certain number of times.	○	-
Malfunction Status	The accumulator pressure sensor decrease rate exceeds a certain threshold a certain number of times.	-	○
Detection Time		-	-
Number of Trips		1 trip	1 trip

HINT:

DTC will be output when conditions for either of the patterns in the table above are met.

CAUTION / NOTICE / HINT

NOTICE:

After replacing the brake actuator (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.	READ VALUE USING TECHSTREAM (SERVO PRESSURE)

(a) Select the Active Test on the Techstream.

Click here

Chassis > ABS/VSC/TRAC > Active Test

Tester Display	Measurement Item	Control Range	Diagnostic Note
ECB Solenoid (SLR)	Linear solenoid reduction valve (SLR)	Solenoid ON/OFF	ECB: Electronically Controlled Brake System

Chassis > ABS/VSC/TRAC > Data List

Tester Display	Measurement Item	Range	Normal Condition	Diagnostic Note
Servo Pressure	Pressure value of servo	Min.: 0.00 MPa, Max.: 24.48 MPa	Brake pedal released: 0.00 to 2.10 MPa	Brake pedal is being depressed: Changes in proportion to the depression force of the brake pedal

Chassis > ABS/VSC/TRAC > Active Test

Active Test Display
ECB Solenoid (SLR)

Data List Display
Servo Pressure

(b) Perform the Active Test and operate the linear solenoid (SLR) in the brake actuator (brake booster with master cylinder assembly).

OK:

The servo pressure output value does not increase when performing the Active Test.

HINT:

If the servo pressure output value increases, an internal brake fluid leak in the brake actuator (brake booster with master cylinder assembly) is suspected.

Result	Proceed to
The servo pressure output value increases.	A
The servo pressure output value does not increase.	B

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

2.	CHECK OPERATING TIME OF PUMP MOTOR

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

(b) Select the Data List on the Techstream.

Click here

Chassis > ABS/VSC/TRAC > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

MT Voltage Value

MT voltage value

Min.: 0.00 V, Max.: 20.00 V

Pump motor off: 0.00 V

Pump motor on: 12.00 V

Chassis > ABS/VSC/TRAC > Data List

Tester Display
MT Voltage Value

OK:

The pump motor operates once or more within 20 seconds or operates for 10 seconds or more each time.

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

3.	CHECK FOR FLUID LEAK

(a) Check for brake fluid leaks in the line from the brake booster pump assembly to the brake booster with master cylinder assembly.

Click here

OK:

There are no brake fluid leaks.

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY AND BRAKE BOOSTER PUMP ASSEMBLY

for the brake booster with master cylinder assembly: Click here

for the brake booster pump assembly: Click here

REPAIR MALFUNCTIONING PART