Make, model, year, etc would help. I'm assuming this is a car.
Look for wires going to all 4 wheels, don't confuse the brake rubber flex hoses for wires. For each wheel that has a wheel speed sensor it will have to have wires going from the sensor to the body and then on to the ABS computer.
Two wheel abs will only have wheel speed sensors in the rear. Four wheel abs will have wheel speed sensors at all four wheels.
Tell me the year and I can tell you the answer.
The DX and LX models with the 4 cylinder engine have front disc and rear drum brakes. The LX and EX models with the V6 engine have four wheel disc brakes. You can tell these cars at a glance by their five lug wheel hubs and dual exhaust pipes. The 4 cylinder EX models come with front disc and rear drum brakes standard, but if they are equipped with antilock brakes (ABS) then they come with four wheel disc brakes.
It sends a signal to the computer that tells how fast you are going. It also works with the antilock brakes. They can be located on the engine, transmission, transfer case, axle, or wheel bearing hub. Its job is to tell a computer how fast a component is turning.
There will be a wire running to a sensor at the front wheel bearings on both sides. No wire to the bearing, no front abs.
Rear wheel abs was standard equipment on a 2007 Dodge Dakota. Four wheel abs was optional. If you have wiring going to the front wheel bearings for sensors, it is four wheel abs.
4 wheel ABS brakes are standard on the Mercury Mountaineer in 1999
Your 1991 Cadillac Deville has 4 wheel anti-lock disc brakes.
Put the key in the ignition. Turn key to"Run". A slew of warning lamps will come on. If you see one light up that looks like this: (ABS) - then the vehicle has an Anti-lock Braking Systen.
you can contact any dodge dealer and give them the last 8 digits of your vin and the can tell you everything you have on that car.
Look for speed sensor wiring at the front wheel bearings. If you have front speed sensors, you have abs.
Rear brakes do not have to be replaced too often. It's really hard to tell without looking at it. What you can do is to replace front brakes and test drive it, if you feel that your car brakes works just fine you do not need to replace rear brake shoes.