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Why is my dash board "Brake" indicator light on and how can it be reset (yes the e-brake is off)?

Did a brake fluid flush and bleed today and when I took it for a test drive noticed that the "Brake" indicator light was on. I tried to raise and release the e-brake, but nothing changed.

Please provide a link to the brake fluid change post if you have it.

Thanks in advance!

 

There is no way to "reset" the brake warning light, there is a fault that needs to be corrected. The typical reasons could be that either the handbrake is engaged or there is insufficient fluid in the brake master cylinder reservoir. Since you report that your handbrake is down, please immediately check and confirm that you have a sufficient amount of fluid in the reservoir. The fluid level should be between the MIN and MAX marks, and I fill mine close to the MAX mark after a fluid change.

Alternative reasons include a faulty emergency brake switch and a faulty reservoir float. If you didn't remove the center console, I doubt that it's the e-brake switch. There has been one local member that had a master cylinder reservoir float that didn't float, indicating a fault even though the reservoir was full. However, that is a rare occurrence and I suspect that either you didn't fill the reservoir enough or that you have a leak that has allowed the fluid level to drop. Since the braking system is the most important system on the car I'd make every effort to find and fix the problem immediately.

 

Well, I turned on my brain, found the circuit diagram and found (like CoralDoc said) the two switches (e-brake and brake fluid float). When they are closed (e-brake up or float down) the indicator light comes on. My brake fluid level is at max, just filled it after doing the flush/bleed.

• Blocked rear wheels, released the e-brake, started engine
• To test I unplugged the harness at the float switch (located on the side of the brake fluid reservoir) and the brake light went off!
• Re-installed the plug, indicator came back on
• Removed cap and fill screen from brake fluid resevior
• Using small screw driver gently nudged the brake fluid float and checked brake indicator light, still on
• Gently pried up on edge of float with screw driver and it raised, brake light now off
• As a check I pushed the float down with the screw driver and brake indicator light turned on, released and it went off again
• Re-installed fill screen and cap

Somehow the float got stuck in the down position after I extracted the old fluid from the reservoir. Simple problem, once I engaged my brain, maybe this will help someone else some day.

 

Yeah. Assuming you have fluid, a stuck float is almost always the answer.

 

Thank you Random1,

I just did a complete brake job. Replaced rotors, pads and flushed brake fluid. When I was on my test drive, I noticed the "brake" light was on.

I decided to reset the ECU in hopes that it would clear, but to no avail.

I read your post and unplugged the harness at the float switch. Re-installed and the problem is cleared up. That was easier than I could have hoped for, and didn't even have to go to the next step of messing with the float.

Good job, and thanx again.
Hockey

 

I don't have a manual or schematic handy, so please forgive me if the answer to this question is obvious.

I'm about to do a brake and clutch fluid change on my S2000. When I remove the dirty brake fluid from the reservoir, the float switch will close. That should not send a signal to the ECU and report a brake fault if power is not applied to the vehicle while the switch is closed. As long as the float does not stick when the reservoir is filled, no brake system fault light should illuminate when I start the car...correct?

When I bleed the brakes, I assume that there is no reason to have the car running as my helper pumps the pedal. I've done brake bleeds on other vehicles and there was no problem doing the job with the engine off. I can't remember any mention of whether the engine should be running or not in the "how to" stickies regarding replacing the brake fluid in the S2000.

 

No need to have the engine running or the key on during a brake bleed.

BTW, the brake fluid level is used as an indicator of pad thickness, so only re-fill to MAX if you have like-new thickness pads. Thay way, when your pads wear down, the fluid level will go below MIN, and the float siwtch will cause the dash Brake light to illuminate, reminding you that you're about out of pads.

If you fill to MAX with worn pads, not only will you not get this warning, but when you retract the pistons to install new pads, your brake fluid may overflow.

Ted

 

I disagree with your advice Tedster. I always maintain my brake fluid near the MAX line in the reservoir and independently inspect my brake pads for wear. Using the brake reservoir level as a pad thickness indicator is indirect and can give the misleading impression that your pads are OK. If one set of pads wears more quickly than another (either due to differences front to rear, or to faulty or sticky pads) you will not know about it until you're on the backing plates. As you mention, if the fluid is filled with anything other than new pads, you may need to remove fluid before retracting the pistons or the reservoir may overflow.

I do agree that it isn't necessary to have the key on or engine running when you change brake fluid. The brake light is actuated by the 2 simple switches, one in the master cylinder float and the other next to the emergency brake handle. If either one doesn't close, the light comes on. As soon as the switch opens, the light goes off. This is unlike other indicator lights in the dash, like the ABS, SRS and Check Engine lights that may throw a code in the ECU and may need to be "cleared".

 

Joshua,

I agree that the fluid level shouldn't be relied on as the only indication of brake pad condition!

I just think that filling to MAX with worn pads both eliminates a source of warning/reminder, and leads to possible overflow. I have had the light come on during a track session, when a set of BrakeMan #3 pads wore out much quicker than expected...

 

OK, this answers my question about the operation of the brake light in respect to the float switch in the brake master cylinder reservoir. Other respondents confirmed that there is no need to start the car to bleed the brakes (I didn't think so, but the threads about the brake warning light and attempts to reset the ECU led me to believe that some mechanism triggered a code in the ECU...implying the electrical system was somehow powered). Thanks folks! I really appreciate the help.