DTC P0504-2B: Brake Switch "A"/"B" Signal Cross Coupled [11/2021 - ]: Description
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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 GTS, Data List item Stop Light SW is ON when the brake pedal is depressed.
| DTC No. | Detection Item | DTC Detection Condition | Trouble Area | MIL | Note |
|---|---|---|---|---|---|
| P0504-2B | Brake Switch "A"/"B" Signal Cross Coupled | Conditions (a) and (b) are met for 0.5 seconds or more (1 trip detection logic): (a) Ignition switch ON (b) STP signal OFF when ST1- signal OFF |
|
Does not come on | SAE Code: P0504 |