DTC P0504: Brake Switch "A" / "B" Correlation; DTC P0724: Brake Switch "B" Circuit High: Description
WARNING: This page is about a different variant/trim than selected.
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 or 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 the Techstream.
| Signals | Brake Pedal Released | In Transition | Brake Pedal Depressed |
|---|---|---|---|
| STP | OFF | ON | ON |
| ST1- | ON | ON | OFF |
- [OFF] denotes ground potential.
- [ON] denotes battery potential (+B)
- On the Techstream, both the Data List items Stop Light Switch and ST1 are ON when the brake pedal is depressed because the ST1 indication characteristic is opposite to the Stop Light Switch indication.
| DTC No. | DTC Detection Condition | Trouble Area |
|---|---|---|
| P0504 | Conditions (a), (b) and (c) continue for 0.5 seconds or more (1 trip detection logic): (a) Ignition switch on (IG) (b) Brake pedal released (c) STP signal OFF when ST1- signal OFF |
|
| 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) |
|