So one of my trucks has always had the ABS light on, and about a month ago I replaced the ABS wheel speed sensor thing that sits in the top of the rear differential and the light went away. Now recently I was having a bunch of electrical gremlins, including lack of 4x4, that I traced back to the GEM module. I replaced the GEM module on Friday the 23rd, and now the ABS light is back on, though everything else works as it should. Is it possible for the sensor I changed to have gone bad already? Or did I mess something up when changing the GEM module?

Any suggestions would be appreciated, Thanks. I did replace the Wheel Speed Sensor with a Dorman Part, if that matters at all.

 

When I replaced the GEM in my Expedition, I had to reset the ABS light with my scanner after a GEM removal and reinstall. I never really looked into the why's of it, because it was able to be reset.

 

Thanks White, I'll have to try that.

 

Did you ever test the sensors?
Did you ever pull the ABS code?
You need to do these things, otherwise you are throwing money at the problem.

 

I'm not sure how to test the sensor, but when I installed it a month ago it cost me $7....so im not out much money. And when the ABS light first popped on after the GEM swap, I threw my code reader on it and got nothing...so I'll have to borrow a nicer one from a buddy...It's free to try to clear a code.

Also, when I replaced the sensor, the ABD light went out immediately, and the light never turned back on until the GEM swap. I dont mind swapping it again, I just wanted to do research about it first.

 

I have a problem with my ABS control module too. I'm getting a c1095. I replaced the ABS control module and pump, but that didn't make the ABS light go away.... Not sure what else to do.

 

The GEM should have nothing to do with the ABS light. You need to know what the ABS code is, and need a decent code reader to get it. Basic ones only pull OBD II codes.
It could be the sensor, it could be the ABS control module, it could be wiring, it could be the tone rings. Hard to say without a code.

Also, get a Motorcraft sensor, in the long run it is cheaper. I got one for I think $25. If you were local to me, I have one you could have for free.

Again, have you tested the ABS sensors? Pretty easy to check with an Ohm meter. Don't remember the values off hand, but for the front, just pull the plug in the wheel well with the tire jacked up and spin it, see what it reads. Rear is a little harder since both tires need to be off the ground, but similar check.

 

do you need some kind of an oscilloscope to read abs signals? or can you use an ohm meter if you spin the wheel slow? how is that done with a meter? thanks

 

i think you can do it with just a multimeter.

 

You just need an ohm meter.
Unplug the sensor (front one's are at the shock tower, rear is top of axle). Put your leads in the sensor (only 2 wires, does not matter which one).
Front ones are easy, just jack up the tire and spin it. You will get a reading in ohms. Value is available online. Rear you have to jack the entire rear end up to spin the tires.
You don't have to get it going fast, just enough to get a stead reading to get the max.