Lexus IS250 · Service Manual BRAKE

C1251/51

Diagnostic trouble codes

DESCRIPTION

DTC No.
 DTC Detection Condition
 Trouble Area
C1251/51
  1. Actuator pump motor does not operate properly.
  2. Open in actuator pump motor circuit continues for at least 2 seconds.
  1. Brake actuator assembly (GND circuit)
  2. Brake actuator assembly (Motor circuit)

WIRING DIAGRAM

C109434E01

INSPECTION PROCEDURE

NOTICE:
When replacing the brake actuator assembly, perform zero point calibration (Click here).


1. PERFORM ACTIVE TEST BY INTELLIGENT TESTER (ABS MOTOR RELAY)

  1. Connect the intelligent tester to the DLC3.

  1. Start the engine.

  1. Select the Active Test mode on the intelligent tester.

  1. Check the operating sound of the ABS motor relay and motor when operating it with the intelligent tester.

    ABS / VSC: 
    Item (Display)
    		 Vehicle Condition / Test Details
    		 Diagnostic Note
    Motor Relay
    		 Turns ABS motor relay ON / OFF
    		 Operating sound of relay (clicking sound) and motor can be heard

    OK:
    The operating sound of the ABS motor relay and motor can be heard.



 OK
Go to step 3
NG


2. INSPECT SKID CONTROL ECU (GND2 TERMINAL)

  1. F049362E32
    Turn the engine switch off.

  1. Disconnect the skid control ECU connector.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    A14-1 (GND2) - Body ground
    		 Always
    		 Below 1 Ω



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR (GND2 CIRCUIT)
OK


3. RECONFIRM DTC

  1. Reconnect the skid control ECU connector.

  1. Clear the DTC (Click here).

  1. Start the engine.

  1. Drive the vehicle at the speed of 4.3 mph (7 km/h) or more.

  1. Check if the same DTC is recorded (Click here).

    Result:
    Condition
    		 Proceed to
    DTC (C1251/51) is not output
    		 A
    DTC (C1251/51) is output
    		 B

    HINT:
    1. If a speed signal of 4 mph (6 km/h) or more is input to the skid control ECU, with the engine switch on (IG) and the stop light switch off, the ECU performs self diagnosis of the motor and solenoid circuits.
    2. If a normal system code is output (trouble code is not output), slightly jiggle the connectors, wire harness, and fuses of the brake actuator assembly. Make sure that no DTCs are output.
    3. If any DTCs are output while jiggling a connector or wire harness of the brake actuator assembly, inspect and repair the connector or wire harness.



 B
REPLACE BRAKE ACTUATOR ASSEMBLY
A

USE SIMULATION METHOD TO CHECK


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