Skip the auto shop - Our mechanics make house calls

Q: Brake lights work when vechile is off. They quit when you start it

asked by on

just put a different motor in the 94 gmc it come out of a 89 chevy van first it had a issue of to much gas change temp sensor idle air control vavle throttle position sensor egr vavle knock sensor still the same come to find out change computer it come out of it noiw the issue with the brake lights if vechiles not started they work the minute you start it they quit tail lights work find blinkers work find

My car has 132678 miles.
My car has a manual transmission.

There may be a fault in the brake light switch or corrosion crossing a circuit and making the lights work backwards. This switch is usually found on the brake pedal, but a technician with access to a wiring diagram should check the whole circuit for any other issues like loose connections or corrosion that may cause high resistance. Consider having an experienced technician, like one from YourMechanic, come out and take a closer look at the brake lighting to offer a more personal diagnosis.

Was this answer helpful?

Need advice from certified mechanic? Get help now!

Over 1000 mechanics are ready to answer your question.
The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing

Get a quote

What others are asking

Q: brake lights stay on when driving

Hello. If your brake lights are staying on, even after a new stop light switch has been installed then it may be possible that there is an issue elsewhere. It does not appear that this model of vehicle requires any...

Q: Battery dying after sitting in 2001 GMC Jimmy

Hi there. There may be a parasitic draw on the battery. This can be checked by inserting a digital multimeter set to ohms inline with the negative battery cable. Generally, the current draw should not exceed 50 milliamps one hour...

Q: O2 sensor or EGR valve?

Hi There, There are a few situations that may cause the O2 sensor to produce a false reading. As you may know the [oxygen sensors]((https://www.yourmechanic.com/services/oxygen-sensor-replacement) which are part of your emissions system read exhaust gases to determine whether or not...

Related articles

What Causes Hoses to Leak?
While the largest part of your engine is mechanical, hydraulics plays a significant role. You’ll find fluids at work in a number of different areas. Your car's fluids include: Engine oil Transmission...
P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the...
How to Avoid Back Pain in a Car
If you have back problems, sitting in a car for an extended period of time can be excruciating. Even without back problems, you could experience discomfort and soreness from...