Lexus ES: Brake Control Warning Light Remains ON
DESCRIPTION
The skid control ECU (brake booster with master cylinder assembly) is connected to the combination meter assembly via CAN communication.
If the skid control ECU (brake booster with master cylinder assembly) stores a DTC, the brake warning light / yellow (minor malfunction) comes on in the combination meter assembly.
WIRING DIAGRAM
CAUTION / NOTICE / HINT
NOTICE:
After replacing the skid control ECU (brake booster with master cylinder assembly), perform linear solenoid valve offset learning, ABS holding solenoid valve learning, yaw rate and acceleration sensor zero point calibration and system information memorization after performing "Reset Memory".
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PROCEDURE
| 1. | CHECK CAN COMMUNICATION SYSTEM |
(a) Check if CAN communication system DTCs are output.
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| Result | Proceed to |
|---|---|
| DTCs are not output. | A |
| DTCs are output. | B |
| B |  | INSPECT CAN COMMUNICATION SYSTEM |
|
| 2. | CHECK IF BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY CONNECTOR IS SECURELY CONNECTED |
(a) Check if the skid control ECU (brake booster with master cylinder assembly) connector is securely connected.
OK:
The connector is securely connected.
| NG | | CONNECT CONNECTOR TO BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY CORRECTLY |
|
| 3. | CHECK AUXILIARY BATTERY |
(a) Check the auxiliary battery voltage.
Standard Voltage:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| Auxiliary battery | Power switch on (IG) | 11 to 14 V |
| Auxiliary battery | Power switch on (READY) | 11 to 15.5 V |
| NG | | CHARGE OR REPLACE AUXILIARY BATTERY |
|
| 4. | READ VALUE USING TECHSTREAM (BRAKE WARNING LIGHT / YELLOW (MINOR MALFUNCTION)) |
(a) Select the Data List on the Techstream.
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| Tester Display | Measurement Item | Range | Normal Condition | Diagnostic Note |
|---|---|---|---|---|
| ECB Warning Light | Brake warning light / yellow (minor malfunction) | ON or OFF | ON: Warning light on OFF: Warning light off | ECB: Electronically Controlled Brake System |
| Tester Display |
|---|
| ECB Warning Light |
(b) Check the Techstream display condition of the brake warning light / yellow (minor malfunction).
| Result | Proceed to |
|---|---|
| ON is displayed. | A |
| OFF is displayed. | B |
| A | | REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY |
| B | | INSPECT METER / GAUGE SYSTEM |
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