DTC P0504: Brake Switch "A" / "B" Correlation [03/2019 - 09/2022]: Description
WARNING: This page is about a different car, the 2022 Toyota Corolla, 2021 Toyota Corolla, 2020 Toyota Corolla, and 2019 Toyota Corolla. However, it is still accessible from the selected car via links, so may be relevant.
The stop light switch assembly 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 assembly and stores this 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. | Detection Item | DTC Detection Condition | Trouble Area | MIL | Memory | Note |
|---|---|---|---|---|---|---|
| P0504 | Brake Switch "A" / "B" Correlation | Conditions (a) and (b) continue for 0.5 seconds or more (1 trip detection logic): (a) Ignition switch ON (b) STP signal is off when ST1- signal is off |
|
Does not come on | DTC stored | DTC for Mexico Models - Applies |