DTC P0504: Brake Switch "A" / "B" Correlation [08/2015 - 08/2019]: Description
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 stores the DTC.
HINT:
The normal signal conditions are as shown in the table below.
| Signal (ECM Terminal) | 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) Engine switch is on (IG). (b) Brake pedal is released. (c) STP signal is OFF when the ST1- signal is OFF. |
|