Lexus IS250 · Service Manual BRAKE

Brake Warning Light Remains ON

Circuit diagnosis

DESCRIPTION

The skid control ECU is connected to the combination meter via CAN and multiplex communications.
If any of the following is detected, the BRAKE warning light remains on:
  1. The skid control ECU connector is disconnected from the skid control ECU.
  2. The brake fluid level is insufficient.
  3. The parking brake is applied.
  4. The EBD is defective.

WIRING DIAGRAM

C114547E01

INSPECTION PROCEDURE

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


1. CHECK CAN COMMUNICATION SYSTEM

  1. Check if the CAN communication system DTC is output (Click here for LHD, or Click here for RHD).

    Result:
    Condition
    		 Proceed to
    DTC is not output
    		 A
    DTC is output
    		 B



B
INSPECT CAN COMMUNICATION SYSTEM
A


2. CHECK MULTIPLEX COMMUNICATION SYSTEM

  1. Check if the multiplex communication system DTC is output (Click here).

    Result:
    Condition
    		 Proceed to
    DTC is not output
    		 A
    DTC is output
    		 B



B
INSPECT MULTIPLEX COMMUNICATION SYSTEM
A


3. CHECK IF SKID CONTROL ECU CONNECTOR IS SECURELY CONNECTED

  1. Check if the skid control ECU connector is securely connected.

    OK:
    The connector should be securely connected.



 NG
CONNECT CONNECTOR TO ECU CORRECTLY
OK


4. CHECK BATTERY

  1. Check the battery voltage.

    Standard voltage:
    11 to 14 V



 NG
CHECK AND REPLACE CHARGING SYSTEM OR BATTERY
OK


5. INSPECT SKID CONTROL ECU (IG1 TERMINAL)

  1. F049362E33
    Disconnect the skid control ECU connector.

  1. Turn the engine switch on (IG).

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

    Standard voltage:
    Tester Connection
    		 Condition
    		 Specified Condition
    A14-46 (IG1) - Body ground
    		 Engine switch on (IG)
    		 10 to 14 V



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR (IG1 CIRCUIT)
OK


6. INSPECT SKID CONTROL ECU (GND TERMINAL)

  1. F049362E34
    Turn the engine switch off.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    A14-32 (GND1) - Body ground
    		 Always
    		 Below 1 Ω
    A14-1 (GND2) - Body ground
    		 Always
    		 Below 1 Ω



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


7. INSPECT PARKING BRAKE SWITCH

  1. C109430E01
    Disconnect the parking brake switch connector.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    1 - Body ground
    		 Parking brake switch ON
    (Switch pin free)
    		 Below 1 Ω
    1 - Body ground
    		 Parking brake switch OFF
    (Switch pin pushed in)
    		 10 kΩ or higher



NG
REPLACE PARKING BRAKE SWITCH
OK


8. CHECK HARNESS AND CONNECTOR (SKID CONTROL ECU - PARKING BRAKE SWITCH)

  1. I045331E05
    Measure the resistance according to the value(s) in the table below.

    Standard resistance:
    A/T:
    Tester Connection
    		 Condition
    		 Specified Condition
    A14-28 (PKB) - A25-1
    		 Always
    		 Below 1 Ω
    A14-28 (PKB) - Body ground
    		 Always
    		 10 kΩ or higher
    M/T:
    Tester Connection
    		 Condition
    		 Specified Condition
    A14-28 (PKB) - J88-1
    		 Always
    		 Below 1 Ω
    A14-28 (PKB) - Body ground
    		 Always
    		 10 kΩ or higher



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


9. INSPECT BRAKE FLUID LEVEL WARNING SWITCH

  1. C109437E01
    Remove the reservoir tank cap and strainer.

  1. Disconnect the brake fluid level warning switch connector.

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

    HINT:
    A float is placed inside the reservoir. Its position can be changed by increasing/decreasing the level of brake fluid.

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    1 - 2
    		 Float up (Switch OFF)
    		 1.9 to 2.1 kΩ
    1 - 2
    		 Float down (Switch ON)
    		 Below 1 Ω

    HINT:
    If there is no problem after finishing the above check, adjust the brake fluid level to the MAX level.



 NG
REPLACE BRAKE MASTER CYLINDER RESERVOIR SUB-ASSEMBLY (BRAKE FLUID LEVEL WARNING SWITCH)
OK


10. CHECK HARNESS AND CONNECTOR (COMBINATION METER - BRAKE FLUID LEVEL WARNING SWITCH)

  1. C114550E01
    Disconnect the combination meter connector.

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

    Standard resistance:
    Tester Connection
    		 Condition
    		 Specified Condition
    J35-15 (SW) - A16-1 (+)
    		 Always
    		 Below 1 Ω
    J35-15 (SW) - Body ground
    		 Always
    		 10 kΩ or higher
    A16-2 (E) - Body ground
    		 Always
    		 Below 1 Ω



NG
REPAIR OR REPLACE HARNESS OR CONNECTOR
OK


11. INSPECT COMBINATION METER ASSEMBLY

  1. Perform Active Test of the combination meter (meter CPU) using the intelligent tester (Click here).

    OK:
    The BRAKE warning light turns on or off in accordance with the intelligent tester.

    HINT:
    1. Reinstall the connectors and restore the vehicle to its prior condition before checking the combination meter.
    2. If troubleshooting has been carried out according to the Problem Symptoms Table, refer back to the table and proceed to the next step before replacing the part (Click here).



 NG
REPLACE COMBINATION METER ASSEMBLY
OK

REPLACE BRAKE ACTUATOR ASSEMBLY


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