What to Read Next

Why do my brake warning lights keep coming on?

Ben Wojdyla
14 May 2013

Q: I recently bought a 2000 Chevy 1500 pickup. The brake and ABS warning lights come on intermittently while driving, but the brakes seem to work fine. The previous owner said it had done this for several years, even after having a brake job. What are the possible causes?

MORE AT POPULAR MECHANICS

A: This sounds to me like a case where the hardware that makes the truck stop is just fine (master cylinder, brake lines, calipers, pistons, pads, and rotors), and the problem lies in the sensors used to trigger the antilock braking system. All brake systems default to manual function when something goes haywire with the electronic enhancements, which is why the brakes seem to work just fine. Slam on the brakes hard and I bet they lock up, which is not what should happen.

The likely culprit is one of the ABS wheel-speed sensors, a pinky-size part that detects the teeth of the tone ring. The tone ring looks like a gear and hooks to the axle hub; the wheel-speed sensor "sees" the teeth and can determine how fast the wheel is moving. If the sensor is dirty, out of alignment, broken, or not putting out enough electrical signal, the computer can't determine what that wheel is doing, so it puts up the warning light. A scan tool might even tell you which sensor is acting up. You might need to remove the caliper and rotor to access the sensors to inspect and clean each one, so it's going to be an afternoon job.

If you find anything amiss, such as a broken or worn wire harness or sensor, replace without trying to salvage things. Put everything back and remove the positive battery cable for a half-hour to reset the computer. Drive around and see if the warning comes back. If it does, consider taking the truck to a reputable brake shop. It might sting the pocketbook a bit, but so will failing to stop fast enough in an emergency.

[Related: 12 Surprising Cars Under $30K]

Transfer Your Balance To A Better Credit Card

CreditCards.com makes it easy to compare the top ranked credit cards out there. Learn more about balance transfer credit cards here.

Earn A More Flexible Online Degree At Capella

With no set deadlines or required seat time, FlexPath helps you earn a degree at the speed that's right for you. Start now.

Insane Navy Seal Flashlight, should it be banned?

The Military has recently released technology that is now available to the public. Get yours before they run out - Limited Supply!

What Happens When a Harvard Engineer Gets Robbed?

He designs a smarter home security system—without contracts, installation fees or sneaky salesmen. Discover a smarter way to protect your home today.

Banks Are Worried Homeowners Will Do This.

Homeowners are surprised and furious. If you owe less than $625,000 on your home, you better read this.

Thousands of $2 Deals!

Shop the coolest gifts and goods starting at just $2. Find the hottest brand name toys, stocking stuffers, kitchenware, stationery, and much more!

How To Make Sagging Skin Look Tight and Lifted

[Watch] The easy and effective way consumers across the country are improving the look of their wrinkled and sagging skin without cosmetic procedures.

Now Is Your Moment

Qualify for 50 Commission-Free Trades

Got the Need for Speed?

Get on the fast track to a great career. Click here to learn more about training at MMI

Starwood Credit Card

Earn 25,000 Bonus Starpoints®! Use toward Award Nights or Flights.

VA Mortgage Rates In 2016

VA Rates as Low as 2.75% (3.028% APR) 15 Year Fixed. Exclusive For Veteran & Military Takes 1 Min!

9 Cards for People Who Have Great Credit

What card offers up to 5% cash back? And which one offers 24/7 concierge service? See the best credit cards of 2016. Apply online, quickly & easily.

Best Hotels Deals in Las Vegas

Enjoy your trip to Las Vegas knowing you got the best deal! Compare hotel prices and find the best deals with trivago!

Bizarre Insurance Claims

Unbelievable, but true. From dancing deer to tortilla-based arsonists, these stories are some of the best we’ve ever heard.