DTC P0504 Brake Switch "A" / "B" Correlation; DTC P0724 Brake Switch "B" Circuit High: Description
WARNING: This page is about a different car, the 2006 Lexus IS 350. However, it is still accessible from the selected car via links, so may be relevant.
The stop light switch is a duplex system that transmits two signals: STP and ST1-. These two signals are used by the ECM to monitor whether or not the brake system is working properly. If the signals, which indicate the brake pedal is being depressed and released, are detected simultaneously, the ECM interprets this as a malfunction in the stop light switch and sets the DTC.
HINT:
The normal conditions are as shown in the table below. The signals can be read using an intelligent tester.
SIGNAL AND BRAKE PEDAL POSITION REFERENCE
| Signal | Brake Pedal Released | In Transition | Brake Pedal Depressed |
|---|---|---|---|
| STP | OFF | ON | ON |
| ST1- | ON | ON | OFF |
DTC DETECTION CONDITION AND TROUBLE AREA
| DTC No. | DTC Detection Condition | Trouble Area |
|---|---|---|
| P0504 | Conditions (a), (b) and (c) continue for 0.5 seconds or more (1 trip detection logic):
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| P0724 | The stop light switch remains ON even when the vehicle is driven in a STOP (less than 2 mph (3 km/h)) and GO (19 mph (30 km/h) or more) fashion 5 times. (2 trip detection logic) |
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