Lexus ES: Brake Hold Operated Indicator Light Circuit
DESCRIPTION
The brake hold operated indicator light illuminates when the brake hold system is operating (vehicle stopped due to brake fluid pressure hold) and turns off when the brake hold system operation is finished (brake fluid pressure decreases).
The brake hold system may not operate depending on vehicle conditions even when the system is in standby mode and the brake hold standby indicator light is illuminated.
If there is a system malfunction that causes brake hold control to be prohibited, when the vehicle is under the following conditions and the brake hold switch (No. 3 combination switch assembly) is pressed, the brake hold operated indicator light blinks.
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Vehicle Conditions:
- The driver door is closed.
- The driver seat belt is fastened.
HINT:
- When the power switch is turned off during brake hold operation, control stops.
-
If brake hold control does not operate even when the vehicle stops, depress on the brake pedal again firmly to stop the vehicle.
If brake hold control still does not operate, confirm the conditions for brake hold control to operate.
CAUTION / NOTICE / HINT
NOTICE:
After replacing the skid control ECU (brake actuator assembly), perform acceleration sensor zero point calibration and store system information memorization.
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PROCEDURE
| 1. | PRE-CHECK |
(a) Check that the brake hold standby indicator light operates normally.
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(b) If the brake hold operated indicator light does not illuminate even though the brake hold standby indicator light is illuminated, check that the following brake hold operation (brake fluid pressure is being maintained ) conditions are met.
- System is in operation standby state (brake hold standby indicator light is illuminated).
- Shift position is not P or R.
- Driver is depressing brake pedal and vehicle is fully stopped.
- Driver is not depressing accelerator pedal.
- Vehicle is not on steep decline.
HINT:
If a malfunction occurs in one of the following systems, the brake hold operated indicator light will blink. If this occurs, perform troubleshooting on the malfunctioning system.
- Brake system
- Electric parking brake system
|
| 2. | CHECK VEHICLE CONTROL HISTORY (ELECTRONICALLY CONTROLLED BRAKE SYSTEM AND ELECTRIC PARKING BRAKE SYSTEM) |
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Enter the following menus: Chassis / Brake/EPB / Utility / Vehicle Control History (RoB).
(d) Using the Techstream, check for Vehicle Control History.
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| Tester Display |
|---|
| Vehicle Control History (RoB) |
HINT:
If vehicle control history is stored when the electronically controlled brake system and electric parking brake system are suspended and the brake hold switch (No. 3 combination switch assembly) is operated with the following vehicle conditions met, the brake hold operated indicator light blinks.
- The driver door is closed.
- The driver seat belt is fastened.
| Result | Proceed to |
|---|---|
| There is no vehicle control history for when the electronically controlled brake system and electric parking brake system were suspended. | A |
| There is vehicle control history for when the electronically controlled brake system and/or electric parking brake system were suspended. | B |
| B |  | PERFORM TROUBLESHOOTING AND REPAIR REGARDING VEHICLE CONTROL HISTORY |
|
| 3. | INSPECT COMBINATION METER ASSEMBLY |
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Enter the following menus: Body Electrical / Combination Meter / Active Test.
(d) Perform the Active Test of the combination meter assembly using the Techstream.
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| Tester Display |
|---|
| Hold Indicator |
(e) Check the combination meter assembly.
OK:
The brake hold operated indicator light turns on or off in accordance with the Techstream operation.
| OK | | REPLACE BRAKE ACTUATOR ASSEMBLY |
| NG | | INSPECT METER / GAUGE SYSTEM |
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