1999 Corolla Brake Problem - Toyota Corolla, Chevy Prizm (1998-2008)

Guest corolla67

I have a 1999 Corolla Automatic Non-ABS

The brake warning light (shared with the parking brake) comes on intermittent while driving. It seems to happen most while the transmission is shifting. So for example accelerating hard from a stop, then letting off gas to force transmission to shift will turn on light. It will remain on for 2-4 seconds usually, and ive found if i play with the pedal I can make it stay on longer.

The brakes seem to still work fine while the light is on, Ive been able to stop at highway speeds while it is on.

Problems started to occur a few weeks ago, after I adjusted rear brakes and greased the front sliders. I also replaced spark plugs at this time. I've checked brakes for function and they all work while in the air, also bled the brakes, no leaks of fluid are visible and reservoir is topped up.

Im wondering if it could be a problem with Vacuum?

Any help would be greatly appreciated!

More likely the sensor that registers if the reservoir is full of fluid is making intermittent contact or is faulty. An issue with vacuum will like show up as odd braking behavior (generally the pedal will have little power assist, braking will take more effort). The brake fluid level warning switch plugs into the base of the plastic reservoir - be hard to miss. Disconnect the connector, check for corrosion, and reseat and see if the light still comes up. Bad chassis grounds can also cause headaches - those can be tricky to nail down.