Lexus NX manuals

Lexus NX: Abnormal Leak in Accumulator (C1391)

Lexus NX Service Manual / Brake / Brake Control / Dynamic Control Systems / Electronically Controlled Brake System / Abnormal Leak in Accumulator (C1391)

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

Note

C1391

Abnormal Leak in Accumulator

351

Either of the following is detected:

  • Accumulator pressure sensor input does not increase before braking or while the pump motor is operating.
  • Accumulator pressure sensor input reduction rate exceeds the specification before braking and while the pump motor is not operating.
  • Brake fluid leaks
  • Brake actuator (Brake booster with master cylinder assembly)

    (Malfunctioning internal seal, low gas pressure in accumulator, etc.)

-

CAUTION / NOTICE / HINT

NOTICE:

When replacing the brake actuator (brake booster with master cylinder assembly), perform initialization and calibration of the linear solenoid valve.

Click here

PROCEDURE

1.

CHECK FOR FLUID LEAK

(a) Check that there are no fluid leaks in the brake lines between the brake actuator (brake booster with master cylinder assembly) and the wheel cylinders.

(b) Check that the brakes are not dragging.

OK:

There are no fluid leaks or dragging.

NG

REPAIR OR REPLACE APPLICABLE PART
OK

2.

RECONFIRM DTC

(a) Clear the DTCs.

Click here

Chassis > ABS/VSC/TRAC > Clear DTCs

(b) Turn the power switch off.

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

(d) Check if the same DTC is output.

Click here

Chassis > ABS/VSC/TRAC > Trouble Codes

Result

Proceed to

DTC C1391 is output.

A

DTC C1391 is not output.

B
B

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

A

3.

PERFORM ACTIVE TEST USING TECHSTREAM (SOLENOID VALVE)

(a) Turn the power switch off.

(b) Connect the Techstream to the DLC3.

(c) Turn the power switch on (IG).

(d) 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 (SMC/SRC/SCC)

Switching solenoid valve (SMC/SRC/SCC)

Solenoid ON/OFF
  • Operation sound of solenoid (clicking sound) can be heard
  • ECB: Electronically Controlled Brake System
Chassis > ABS/VSC/TRAC > Active Test

Tester Display

ECB Solenoid (SMC/SRC/SCC)

HINT:

The Active Test can be performed when the following conditions are met.

  • ABS main relay is on.
  • Shift lever is in P.
  • Parking brake is applied.
  • Vehicle speed is 0 km/h (0 mph).

(e) Perform the Active Test of the solenoid using the Techstream.

(f) Select the Data List on the Techstream.

Click here

Chassis > ABS/VSC/TRAC > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Wheel Cylinder Pressure Sensor

Wheel cylinder pressure sensor

Min.: 0.00 V, Max.: 5.00 V

Brake pedal released: 0.10 to 0.90 V

Reading increases when brake pedal is depressed
Chassis > ABS/VSC/TRAC > Data List

Tester Display

Wheel Cylinder Pressure Sensor

(g) Check that the output value of the wheel cylinder pressure sensor does not increase.

OK:

The output value of the wheel cylinder pressure sensor does not increase.

HINT:

If the output value increases, there may be brake fluid leaks in the brake actuator (brake booster with master cylinder assembly).

Result

Proceed to

The output value of the wheel cylinder pressure sensor increases.

A

The output values of the wheel cylinder pressure sensor does not increase.

B
B

REPLACE BRAKE BOOSTER PUMP ASSEMBLY

A

4.

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

(a) Replace the brake actuator (brake booster with master cylinder assembly).

Click here

NEXT

REPLACE BRAKE BOOSTER PUMP ASSEMBLY

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