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.
Click here
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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.
Click here
| 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.
Click here
| 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.
Click here
| 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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Removal
REMOVAL CAUTION / NOTICE / HINT CAUTION: Wear protective gloves. Sharp areas on the parts may injure your hands. HINT:
Use the same procedure for the RH and LH sides.
The procedure listed below is for the LH side.
PROCEDURE 1. REMOVE FRONT SEAT ASSEMBLY LH Click here 2. REMOVE FRONT LOWER
