Lexus NX manuals

Lexus NX: Brake Booster Pump Motor on Time Abnormally Long (C1252,C1253)

Lexus NX Service Manual / Brake / Brake Control / Dynamic Control Systems / Electronically Controlled Brake System / Brake Booster Pump Motor on Time Abnormally Long (C1252,C1253)

DESCRIPTION

The skid control ECU (brake booster with master cylinder assembly) detects decreases in the accumulator pressure according to the data from the accumulator pressure sensor, and then starts and stops the pump motor by operating the motor relay.

DTC No.

Detection Item

INF Code

DTC Detection Condition

Trouble Area

Note

C1252

Brake Booster Pump Motor on Time Abnormally Long

311

The pump motor is operating continuously for 178 seconds or more. (When the relay is malfunctioning for 98 seconds or more.)
  • Short in motor circuit or motor monitor circuit
  • Motor relay stuck
  • Accumulator pressure sensor malfunction in brake actuator (Brake booster with master cylinder assembly)
  • Skid control ECU (Brake booster with master cylinder assembly)

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C1253

Pump Motor Relay

321

322

323

324

325

326

327

328

329
  • INF Code: 321
    • With IG1 terminal voltage 9.5 V or more, the motor drive monitor remains off for 0.2 seconds or more after a motor drive on request.
  • INF Code: 322
    • The motor drive monitor remains on for 2 seconds or more after a motor drive off request.
  • INF Code: 323
    • A skid control ECU (brake booster with master cylinder assembly) internal motor drive logical inconsistency continues for 2 seconds or more.
  • INF Code: 324
    • An open circuit is detected in the skid control ECU (brake booster with master cylinder assembly) internal motor relays 1 and 2.
  • INF Code: 325
    • An open circuit is detected in the skid control ECU (brake booster with master cylinder assembly) internal motor relays 1 and 3.
  • INF Code: 326
    • An open circuit is detected in the skid control ECU (brake booster with master cylinder assembly) internal motor relays 2 and 3.
  • INF Code: 327
    • An open circuit is detected in the skid control ECU (brake booster with master cylinder assembly) internal motor relay 1.
  • INF Code: 328
    • An open circuit is detected in the skid control ECU (brake booster with master cylinder assembly) internal motor relay 2.
  • INF Code: 329
    • An open circuit is detected in the skid control ECU (brake booster with master cylinder assembly) internal motor relay 3.
  • INF Code: 321, 324, 325, 326, 327, 328, 329
    • Open in motor circuit or motor monitor circuit
    • Skid control ECU (Brake booster with master cylinder assembly)
  • INF Code: 322
    • Short in motor circuit or motor monitor circuit
    • Skid control ECU (Brake booster with master cylinder assembly)
  • INF Code: 323
    • Skid control ECU (Brake booster with master cylinder assembly)

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WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

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

    Click here

  • Inspect the fuses for circuits related to this system before performing the following procedure.

PROCEDURE

1.

PERFORM ACTIVE TEST USING TECHSTREAM (ABS MOTOR RELAY)

(a) Connect the Techstream to the DLC3.

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

(c) Select the Active Test on the Techstream.

Click here

Chassis > ABS/VSC/TRAC > Active Test

Tester Display

Measurement Item

Control Range

Diagnostic Note

ECB Motor Relay

ABS motor relay

Relay ON/OFF

ECB: Electronically Controlled Brake System
Chassis > ABS/VSC/TRAC > Active Test

Tester Display

ECB Motor Relay

(d) Select the Data List on the Techstream.

Click here

Chassis > ABS/VSC/TRAC > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

ECB Motor Relay

ABS motor relay

ON or OFF

ON: Relay on

OFF: Relay off

ECB: Electronically Controlled Brake System
Chassis > ABS/VSC/TRAC > Data List

Tester Display

ECB Motor Relay

(e) Check the operating condition of the ABS motor relay when operating it with the Techstream.

Result

Proceed to

ABS motor relay in the Data List turns ON/OFF using the Active Test.

A

ABS motor relay in the Data List does not change using the Active Test.

B
B

GO TO STEP 7

A

2.

INSPECT BRAKE BOOSTER PUMP ASSEMBLY

(a) Turn the power switch off.

*a

Component without harness connected

(Brake Booster Pump Assembly)

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

(c) Disconnect the A51 and A52 brake booster pump assembly connectors.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A51-1 (BM1) - A51-2 (GND1)

Always

Below 10 Ω

A52-2 (BM2) - A52-1 (GND2)

Always

Below 10 Ω

A51-1 (BM1) - A52-2 (BM2)

Always

Below 1 Ω

A51-2 (GND1) - A52-1 (GND2)

Always

Below 1 Ω
NG

REPLACE BRAKE BOOSTER PUMP ASSEMBLY

OK

3.

CHECK HARNESS AND CONNECTOR (GND TERMINAL)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A51-2 (GND1) - Body ground

Always

Below 1 Ω

A52-1 (GND2) - Body ground

Always

Below 1 Ω

*a

Front view of wire harness connector

(to Brake Booster Pump Assembly)
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (GND CIRCUIT)
OK

4.

READ VALUE USING TECHSTREAM (ACCUMULATOR PRESSURE SENSOR)

(a) Reconnect the A51 and A52 brake booster pump assembly connectors.

(b) Connect the Techstream to the DLC3.

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

(d) Select the Data List on the Techstream.

Click here

Chassis > ABS/VSC/TRAC > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Accumulator Sensor

Accumulator pressure sensor

Min.: 0.00 V, Max.: 5.00 V

Specified value: 2.90 to 4.20 V

When brake fluid is stored in the accumulator: Accumulator pressure changes in accordance with volume of fluid stored in the accumulator
Chassis > ABS/VSC/TRAC > Data List

Tester Display

Accumulator Sensor

(e) Depress the brake pedal 4 or 5 times to operate the pump motor.

(f) Wait for 30 seconds without depressing the brake pedal.

(g) Check that the accumulator pressure sensor output value change is within the specified range.

OK:

Accumulator pressure sensor output value change is less than 0.55 V.

NG

GO TO STEP 6

OK

5.

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 (IG).

(d) Check if the same DTC is output.

Click here

Chassis > ABS/VSC/TRAC > Trouble Codes

Result

Proceed to

DTCs C1252 and C1253 are not output.

A

DTCs C1252 and/or C1253 are output.

B
A

USE SIMULATION METHOD TO CHECK

B

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

6.

PERFORM ACTIVE TEST USING TECHSTREAM (SOLENOID VALVE)

(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 (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).

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

(c) 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

(d) 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.

OK

REPLACE BRAKE BOOSTER PUMP ASSEMBLY

NG

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

7.

CHECK HARNESS AND CONNECTOR (MRI TERMINAL)

(a) Turn the power switch off.

*a

Front view of wire harness connector

(to Skid Control ECU (Brake Booster with Master Cylinder Assembly))

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

(c) Disconnect the A57 skid control ECU (brake booster with master cylinder assembly) connector.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A57-1 (MRI1) - Body ground

Always

11 to 14 V

A57-2 (MRI2) - Body ground

Always

11 to 14 V
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (MRI CIRCUIT)
OK

8.

CHECK HARNESS AND CONNECTOR (BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY - BRAKE BOOSTER PUMP ASSEMBLY)

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

(b) Disconnect the A51 and A52 brake booster pump assembly connectors.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A57-29 (MRO1) - A51-1 (BM1)

Always

Below 1 Ω

A57-29 (MRO1) or A51-1 (BM1) - Body ground

Always

10 kΩ or higher

A57-30 (MRO2) - A52-2 (BM2)

Always

Below 1 Ω

A57-30 (MRO2) or A52-2 (BM2) - Body ground

Always

10 kΩ or higher
OK

REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

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SEE MORE:

 Removal

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