Lexus ES: 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 | MIL | Note |
|---|---|---|---|---|---|---|
| C1391 | Abnormal Leak in Accumulator | 351 | Either of the following is detected:
|
| Does not come on | Electronically controlled brake system DTC |
| Vehicle Condition | |||
|---|---|---|---|
| Pattern 1 | Pattern 2 | ||
| Diagnosis Condition | Brake pedal not depressed and pump motor operating. | ○ | - |
| Brake pedal not depressed and pump motor not operating. | - | ○ | |
| Malfunction Status | The accumulator pressure sensor value does not increase a certain number of times. | ○ | - |
| 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".
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PROCEDURE
| 1. | READ VALUE USING TECHSTREAM (SERVO PRESSURE) |
(a) Select the Active Test on the Techstream.
Click here
| Tester Display | Measurement Item | Control Range | Diagnostic Note |
|---|---|---|---|
| ECB Solenoid (SLR) | Linear solenoid reduction valve (SLR) | Solenoid ON/OFF | ECB: Electronically Controlled Brake System |
| 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 |
| 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).
(c) Check that the servo pressure output value does not increase when performing the Active Test.
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 |
| A | .gif) | REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY |
|
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| 2. | CHECK OPERATING TIME OF PUMP MOTOR |
(a) Turn the power switch on (READY).
(b) Select the Data List on the Techstream.
Click here
| 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 | - |
| Tester Display |
|---|
| MT Voltage Value |
(c) With the power switch on (READY), check the operation of the pump motor.
OK:
The pump motor operates once or more within 20 seconds or operates for 10 seconds or more each time.
| NG | | 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.
| OK | | REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY AND BRAKE BOOSTER PUMP ASSEMBLY |
| NG | | REPAIR MALFUNCTIONING PART |
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SEE MORE:
Installation
INSTALLATION CAUTION / NOTICE / HINT for HV Model:
When removing or installing the front disc brake caliper assembly, pushing back the disc brake piston may cause a large clearance between the brake pads and brake disc. When the brake pedal is depressed with a large clearance between the brake pa
Relay
On-vehicle InspectionON-VEHICLE INSPECTION PROCEDURE 1. INSPECT HORN RELAY *a Component without harness connected (HORN Relay) (a) Measure the resistance according to the value(s) in the table below. Standard Resistance: Tester Connection Condition Specified Condition 3 - 5 A
