Lexus NX: Open Circuit in Stop Light Switch Circuit (C1249)
DESCRIPTION
The skid control ECU (brake booster with master cylinder assembly) receives the stop light switch assembly signal and detects the brake pedal operation status.
The skid control ECU (brake booster with master cylinder assembly) has an open detection circuit, which stores this DTC if it detects an open in the stop light input line or ground line of the stop light circuit with the stop light switch assembly off (brake pedal not depressed).
| DTC No. | Detection Item | INF Code | DTC Detection Condition | Trouble Area | Note |
|---|---|---|---|---|---|
| C1249 | Open Circuit in Stop Light Switch Circuit | 231 | When IG1 terminal voltage is 9.5 V or more, an open stop light switch circuit continues for 10 seconds or more. |
| - |
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 STOP LIGHT OPERATION |
(a) Check that the all stop lights come on when the brake pedal is depressed and go off when the brake pedal is released.
OK:
| Condition | Illumination Condition |
|---|---|
| Brake pedal depressed. | On |
| Brake pedal released. | Off |
| NG | .gif) | GO TO STEP 5 |
|
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| 2. | READ VALUE USING TECHSTREAM (STOP LIGHT SWITCH ASSEMBLY) |
(a) Connect the Techstream to the DLC3.
(b) Turn the power switch on (IG).
(c) Select the Data List on the Techstream.
Click here
| Tester Display | Measurement Item | Range | Normal Condition | Diagnostic Note |
|---|---|---|---|---|
| Stop Light SW | Stop light switch assembly | ON or OFF | ON: Brake pedal depressed OFF: Brake pedal released | - |
| Tester Display |
|---|
| Stop Light SW |
(d) Check that the stop light switch assembly display observed on the Techstream changes according to brake pedal operation.
OK:
The Techstream displays ON or OFF according to brake pedal operation.
| NG | | GO TO STEP 4 |
|
| 3. | RECONFIRM DTC |
(a) Clear the DTCs.
Click here
(b) Turn the power switch off.
(c) Turn the power switch on (READY).
(d) Depress the brake pedal several times to test the stop light circuit.
(e) Check if the same DTC is output.
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| Result | Proceed to |
|---|---|
| DTC C1249 is not output. | A |
| DTC C1249 is output. | B |
HINT:
If troubleshooting has been carried out according to Problem Symptoms Table, refer back to the table and proceed to the next step.
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| A | | USE SIMULATION METHOD TO CHECK |
| B | | REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY |
| 4. | CHECK HARNESS AND CONNECTOR (STP TERMINAL) |
| (a) Turn the power switch off. |
|
(b) Make sure that there is no looseness at the locking part and the connecting part of the connector.
(c) Disconnect the A57 skid control ECU (brake booster with master cylinder assembly) connector.
(d) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| A57-33 (STP) - Body ground | Stop light switch assembly on (Brake pedal depressed) | 11 to 14 V |
| A57-33 (STP) - Body ground | Stop light switch assembly off (Brake pedal released) | Below 1.5 V |
HINT:
If troubleshooting has been carried out according to Problem Symptoms Table, refer back to the table and proceed to the next step.
Click here
| OK | | REPLACE BRAKE BOOSTER WITH MASTER CYLINDER ASSEMBLY |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT) |
| 5. | INSPECT STOP LIGHT SWITCH ASSEMBLY |
(a) Check the stop light switch assembly.
Click here
OK:
The stop light switch assembly is normal.
| NG | | REPLACE STOP LIGHT SWITCH ASSEMBLY |
|
| 6. | CHECK HARNESS AND CONNECTOR (STP TERMINAL) |
| (a) Make sure that there is no looseness at the locking part and the connecting part of the connector. |
|
(b) Disconnect the A57 skid control ECU (brake booster with master cylinder assembly) connector.
(c) Measure the voltage according to the value(s) in the table below.
Standard Voltage:
| Tester Connection | Condition | Specified Condition |
|---|---|---|
| A57-33 (STP) - Body ground | Stop light switch assembly on (Brake pedal depressed) | 11 to 14 V |
| A57-33 (STP) - Body ground | Stop light switch assembly off (Brake pedal released) | Below 1.5 V |
| NG | | REPAIR OR REPLACE HARNESS OR CONNECTOR (STP CIRCUIT) |
|
| 7. | RECONFIRM DTC |
(a) Reconnect the A57 skid control ECU (brake booster with master cylinder assembly) connector.
(b) Clear the DTCs.
Click here
(c) Turn the power switch off.
(d) Turn the power switch on (READY).
(e) Depress the brake pedal several times to test the stop light circuit.
(f) Check if the same DTC is output.
Click here
| Result | Proceed to |
|---|---|
| DTC C1249 is not output. | A |
| DTC C1249 is output. | B |
HINT:
-
If troubleshooting has been carried out according to Problem Symptoms Table, refer back to the table and proceed to the next step.
Click here
-
If the lighting system is normal but the DTC is still output, replace the skid control ECU (brake booster with master cylinder assembly).
Click here
| A | | USE SIMULATION METHOD TO CHECK |
| B | | INSPECT LIGHTING SYSTEM |
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