6 SYMPTOMS OF A BAD BRAKE LIGHT SWITCH
The purpose of the brake light switch is to close the electrical circuit to turn on the brake lights. This switch is activated when pressing down on the brake pedal. It’s also used to alert the ABS system, deactivate the cruise control, activate the shift interlock solenoid to allow shifting out of park, and allow the car to turn on in a push-button start system.
location
The location of the brake light switch is usually near the brake pedal assembly.
symptoms
check engine light
The first symptom of a bad brake light switch is a check engine light. You might also have an ABS light. If something is wrong with the brake switch, these codes can pop up:
P0504
P0571
P0752
P0573
Ensure you can access your car's diagnostic codes by acquiring an OBD2 scanner here.
brake lights not working
The second symptom is the brake lights not turning on. If you have a defective switch, there won’t be an electrical current flowing through it to reach the brake lights when pressing the brake pedal. If the electrical current doesn’t reach the brake lights they wont be able to turn on.
brake light don’t turn off
On the flip side, the third symptom is the brake lights staying on all the time. This can happen if the switch is shorted internally. Another reason could be the brake light switch stopper fell off. Not having the stopper will make the switch always stay closed, sending an electrical current to the brake lights at all times. Make sure to get this fixed right away as this can be the reason why your battery is dead the next day.
no start
The fourth symptom is the car wont start. This only applies to cars with a push-button start system since it only works when it detects the brake pedal is applied. A faulty brake switch won’t be able to signal the push button start system when the brake pedal is depressed, leaving you with a no-start.
cruise control failure
The fifth symptom of a bad brake light switch is the cruise control not working. In normal operation, the cruise control gets deactivated when pressing down on the brake pedal. The cruise control gets this information from the brake light switch. If the brake light switch isn’t working properly, then the cruise control won’t either.
stuck in park
The last symptom is your car stuck in park. You’ll be pressing down on the brake pedal trying to shift from park to reverse but it seems to be stuck. Most people don’t know this, however, when you press down on the brake pedal it sends a signal to activate the shift interlock solenoid to allow shifting out of park. This is a safety feature. The problem is when the brake switch isn’t working, there won’t be a signal going to the shift interlock solenoid. This will prevent it from functioning properly, leading to you being stuck in the park position.
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