Lexus NX: Brake 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 any of the following is detected, the brake warning light / red (malfunction) remains on:
- The skid control ECU (brake booster with master cylinder assembly) connector is disconnected from the brake booster with master cylinder assembly.
- The brake fluid level is insufficient.
- EBD operation has been disabled.
WIRING DIAGRAM
CAUTION / NOTICE / HINT
NOTICE:
-
When replacing the skid control ECU (brake booster with master cylinder assembly), perform initialization and calibration of the linear solenoid valve.
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- Inspect the fuses for circuits related to this system before performing the following procedure.
PROCEDURE
| 1. | CHECK DTC |
(a) Check if ABS, VSC and/or electronically controlled brake system DTCs are output.
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| Result | Proceed to |
|---|---|
| DTCs are not output. | A |
| DTCs are output. | B |
| B | .gif) | REPAIR CIRCUITS INDICATED BY OUTPUT DTCS |
|
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| 2. | 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 |
|
| 3. | 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 |
|
| 4. | CHECK AUXILIARY BATTERY |
(a) Check the auxiliary battery voltage.
Standard Voltage:
| Tester Connection | Switch 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 |
|
| 5. | CHECK HARNESS AND CONNECTOR (IG1 TERMINAL) |
| (a) Disconnect the A57 skid control ECU (brake booster with master cylinder assembly) connector. |
|
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(b) Turn the power switch on (IG).
(c) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
| Tester Connection | Switch Condition | Specified Condition |
|---|---|---|
| A57-16 (IG1) - Body ground | Power switch on (IG) | 11 to 14 V |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR (IG1 CIRCUIT) |
|
| 6. | CHECK HARNESS AND CONNECTOR (GND TERMINAL) |
| (a) Turn the power switch off. |
|
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(b) Measure the resistance according to the value(s) in the table below.
Standard Resistance:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| A57-28 (GND) - Body ground | Always | Below 1 Ω |
| A57-27 (GND2) - Body ground | Always | Below 1 Ω |
| A57-26 (GND3) - Body ground | Always | Below 1 Ω |
| A57-25 (GND4) - Body ground | Always | Below 1 Ω |
| A57-24 (GND5) - Body ground | Always | Below 1 Ω |
| A57-23 (GND6) - Body ground | Always | Below 1 Ω |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR (GND CIRCUIT) |
|
| 7. | READ VALUE USING TECHSTREAM (BRAKE WARNING LIGHT / RED (MALFUNCTION)) |
(a) Reconnect the A57 skid control ECU (brake booster with master cylinder assembly) connector.
(b) Connect the Techstream to the DLC3.
(c) Turn the power switch on (IG).
(d) Select the Data List on the Techstream.
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| Tester Display | Measurement Item | Range | Normal Condition | Diagnostic Note |
|---|---|---|---|---|
| Brake Warning Light | Brake warning light / red (malfunction) | ON or OFF | ON: Warning light on OFF: Warning light off | - |
| Tester Display |
|---|
| Brake Warning Light |
(e) Check the Techstream display condition of the brake warning light / red (malfunction).
| Result | Proceed to |
|---|---|
| Display of the Data List remains OFF. | A |
| Display of the Data List remains ON. | B |
| A | | INSPECT METER / GAUGE SYSTEM |
| B | | REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY |
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SEE MORE:
Abnormal Leak in Accumulator (C1391)
DESCRIPTION This DTC is stored if internal or external brake fluid leaks are detected due to improper sealing in the brake actuator (brake booster with master cylinder assembly) or brake booster pump assembly. Internal leaks are suspected if the pump motor operates frequently without braking. DTC
Removal
REMOVAL PROCEDURE 1. REMOVE FRONT WIPER ARM HEAD CAP (a) Using a screwdriver, detach the 3 claws and remove the front wiper arm head cap. HINT:
Tape the screwdriver tip before use.
Use the same procedure for both front wiper arm head caps.
*1 Protective Tape 2. REM
