Well, since no one replied to my various posts on how to determine which wheel sensor is bad. I had to dive in blind and figure it out. And I did... this is what happened:
I have a 2003 Protege 5 hatchback with auto trans and 2 litre engine.
The ABS and Brake light came on and stayed on.
I checked the fluid, and the brakes were working fine.
After some research I figured it was a wheel sensor.
I never worked on one, or even seen one in my life, so this was going to be fun.
The front wheel sensors are located on the rear of the hubs, have 2 wires that go up through the wheel well and into the engine bay.
The connectors are at each corner of the engine bay beside the firewall.
Safely jack up the front of the car.
Put the shifter into neutral so the wheels can spin freely.
Unplug the connector for one of the sensors. We want to test the connector that goes to the sensor !!! We are checking for bad sensors.
There should only be 2 wires on the connector.
You will need a multimeter for this.
The sensors are nothing more than a long wire coiled at the end. There should be no shorts to ground.
Verify this by metering the resistance of each wire to chassis ground. There should be NO SHORTS.
Now, meter the resistance between the 2 wires on the connector. You should read approximately 1400 ohms (1.4 k-ohms).
This should tell you that the sensor itself is fine. But we still don't know if it works. The sensor is placed close to a ring gear and will send pulses out as one of the teeth on the gear passes over the sensor. You can actually see this gear, on the rear hubs anyway.
Ok, to test if all is working, keep the meter attached to the sensor connector and set the meter to AC millivolts. [SEE WARNING BELOW] Spin the tire and you should get around 300 millivolts. Of course you will get a higher or lower reading if you spin the wheel faster or slower.
If you get all these readings, then your sensor is operating correctly and all is well with that one.
Plug your connector back together and go do the other side.
The rear sensors are the same, except it is more difficult to get to the connectors. They are located on the side walls behind the back seats and you will have to remove all the plastic panels in your trunk to gain access to them.
My 2 front ones checked out fine and now I was working on my rear drivers side sensor. When I metered the 2 wires, I was expecting 1.4kohms... I got zero. When I spun the wheel, I got no AC voltage.
The rear sensor has 1 bolt holding it onto the hub. I removed the bolt, but the sensor was still stuck tight inside. I put some oil on it and took a pair of vise grips to the metal bracket, NOT the plastic part of the sensor, and slowly twisted it back and forth until it came out. The end of the sensor was full of crap and rust. I took a little wire brush and gently cleaned it until it was shiny and clean. Before putting it back in the hub, I metered it and it showed 1.4kohm again. I suspected that the contamination on it was shorting it to ground. I put the sensor back onto the hub and bolted it down. I spun the wheel and I got 300 millivolts AC.
I plugged the connector back together, backed it out of the garage and the ABS and Brake lights immediately went out. I installed all the plastic panels in the trunk and the car is functioning normally again.
I hope it works as well for you as it did for me.
Warning: Watch your fingers when you spin the tire. Do it by the rubber, not the rim. Someone is going to get their fingers jammed between the spoke of the rim and the brake caliper. That will probably hurt a lot and I will get the blame for it. Do it safely.
