Lexus NX: 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)	-
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)	-

WIRING DIAGRAM

CAUTION / NOTICE / HINT

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.

(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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