Skip the auto shop - Our mechanics make house calls

What Sensors Make the ABS Work?

ABS system sensors

When we are discussing ABS systems it is good to note the year and make of your vehicle because ABS systems have evolved quite a bit over the years, but you also have to know how the ABS system works.

An anti-lock braking system or anti-skid braking system (ABS) is a system that allows the wheels on a motor vehicle to maintain tractive contact with the road surface according to driver inputs while braking, preventing the wheels from locking up and avoiding uncontrolled skidding. It is a computerized system that monitors all the wheels and applies the brakes. It does this at a much faster rate and with better control than a driver could manage.

ABS generally offers improved vehicle control and decreases stopping distances on dry and slippery surfaces; however, on loose gravel or snow-covered surfaces, ABS can significantly increase braking distance, although still improving vehicle control.

The first anti-lock brake systems started out with only having an ABS module (computer), an ABS hydraulic system built into the brake master cylinder, and only had one sensor built into the rear differential of a rear-wheel drive vehicle; this was known as RWAL anti-lock brakes. Automobile manufacturers then went on to put two ABS sensors on the rear wheels and made the hydraulic valving separate from the master cylinder.

Then the anti-lock brake system evolved to having one ABS sensor per wheel, a more sophisticated hydraulic valving system, and computers that would network with each other. Today, the vehicle may have four sensors, one located at each wheel, or the computer may only use the transmission output speed sensor to activate the anti-lock brakes by making the vehicle downshift the transmission or shut down part of the engine. Most of the vehicles on the road today have four sensors, one at each wheel, that you can see by looking behind the wheel at a wire that comes from the bearing area or the axle, which will most likely be your sensors.

Some of the vehicles today have the wires for the ABS going under the carpet in the interior of the vehicle to keep the wires out of the elements. In other vehicles, you will find the wires along the suspension systems. Some are also built into the wheel bearing assy, and if one goes bad you have to change out the whole bearing assembly. I hope that helps you locate where the sensors may be.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details
Icon-warranty_badge-02

Skip the repair shop, our top-rated mechanics come to you.

At your home or office

Choose from 600+ repair, maintenance & diagnostic services. Our top-rated mechanics bring all parts & tools to your location.

Fair & transparent pricing

See labor & parts costs upfront, so you can book with confidence.

12-month, 12,000-mile warranty

Our services are backed by a 12-month, 12,000-mile warranty for your peace of mind.

Get A Quote

Need Help With Your Car?

Our certified mobile mechanics make house calls in over 2,000 U.S. cities. Fast, free online quotes for your car repair.

GET A QUOTE

More related articles

Symptoms of a Bad or Failing Flexible Clutch Hose
Common signs include difficulty shifting, low clutch fluid, and feeling no resistance at the clutch pedal.
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 P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
Insurance Requirements for Car Registration in Kentucky
The Kentucky Transportation Cabinet requires that all drivers in Kentucky carry liability automotive insurance, or “financial responsibility” in order to operate a vehicle legally and maintain vehicle...


Related questions

Q: 95 Civic will not start it cranks but doesn't turn on

The code 3 is for the manifold absolute pressure sensor. These sensors are known to go bad. There are used and cheap aftermarket ones online that do not always fix the problem. I'd recommend using a quality replacement part to...

Q: I have a illuminated Service AdvanceTrac Light and my back passenger rotor is destroyed within minutes of me driving after installation

Hi and thanks for contacting YourMechanic. The AdvanceTrac will need to be adjusted for the height difference. As for the rotor being destroyed after putting on the lift, check the caliper to see if the line to it is long...

Q: Is it safe to drive around without my MAP sensor plugged in?

Hi there. From the description you have provided, your vehicle's drivability concern should be diagnosed and repaired. It is not advisable to drive your vehicle with the MAP (manifold absolute pressure) sensor disconnected. The MAP sensor's job is to determine...