Short story:

- Girlfriend has a 91ish Grand Cherokee 4.0l with ABS light on.

- Replaced front pads/rotors and rear shoes because of wear

- Noticed metal washer magnetically attached to rear wheel speed sensor blocking the sensor pickup wheel.

- Cleaned all sensors and removed all signs of debris.

- Disconnected battery for 30 min and reconnected.

- ABS light still on even after test drive.

How do I read ABS Codes and/or Reset ABS light?

 

Your best bet is to take it somewhere that has the capabiity to read the code (dealer). If they still have the old drb with the correct card then it shouldn't be a problem. Other than that, I don't think that you will get the light out, even by disconnecting the battery.

 

Having the washer on the speed sensor might have done something to the sensor. Putting a metal object right on a permanent magnet like that can sometimes alter the magnetic field, or the washer might have physically damaged the sensor by banging around on it. Those sensors are rugged enough for the elements but don't do well with physical abuse.

 

thanks for the info! is this something i can check my self with a multimeter? or do i just shell out some money to replace the sensor?

 

See if there is any diagnostic capability for that first, I don't really know the specifics of Jeeps, so I can't say. The sensor is difficult to test on its own because it needs power and ground and usually a resistor (between power and signal for a 3-wire sensor) that may be in the sensor or may be in the ABS module. It could be a 2 wire or 3 wire sensor, both of which need different types of testing. So if there is any way to actually diagnose through some other means (fault codes, diagnostic port, etc), that would be easier. It can be tested, yes, but it's not something trivial to do usually, and is best done with an oscilloscope instead of a multimeter, unless you have a pretty high end multimeter. Talk to some shops and see if they have any tricks to diagnosing something like this in your particular vehicle.