I have a 2000 Blazer 4WD 4-door LS that I recently purchased. It has 195K miles on the odometer. It came with a host of issues (intake gasket leak, exhaust leak, needs new tie-rods, idler arm, 4wd vacuum hoses were bad, needed new transfer case vacuum switch, needed tuneup, etc....) but the one issue I cant seem to solve is fixing the ABS light.

The ABS light comes on within a minute or so of driving. Usually I will feel the pulsation of the ABS valves for a few seconds and then the ABS light goes on and my normal braking function (non-ABS) returns. The only dash light is a solid ABS light.....no other dash lights are on. My OBDII scanner does not support ABS so I headed down to Advance Auto Parts and the list of codes is numerous.....the most current codes pointed to the front abs wheel sensors being open and also erratic.

What is the proper method for fixing/finding ABS issues?

-I have replaced the drivers front ABS wheel sensor with new unit
-I replaced the ABS control module with junkyard unit
-I have checked all the fuses
-I have checked all the brake bulbs (I read a thread stating a bad brake bulb can cause issues.
- I checked the 2 front sensors resistance (both ohm to appx 1100 ohms)
- I verified good grounds at G102, G105, G110
- I checked my wheel bearings for excessive play (they have no play)

Are there some diagnostic tips to pinpoint the issue using common tools?
Are there some tests I can perform using a digital multimeter to help pinpoint the problem.

I am about to purchase new wheel hubs assuming the exciter rings are not functioning correctly........but its starting to feel as though I am just grasping in the dark for solutions. Throwing more and more parts at the problem is not the way I want to solve this problem.

Is there a way I can remove all the ABS codes and start fresh? I have an OBDII scanner but it doesnt support ABS. I am relegated to using the auto parts store for the time being to check codes. And they have a company policy that wont allow them to erase the codes on my blazer.

Anyone with a definitive process for diagnosing ABS issues? You will be my new best friend!!! :-)

I am not a mechanic by trade but I am quite experienced on servicing almost any issues on any vehicles.

Also I have ALLDATA on my home computer but that has not been very helpful. The good thing about ALLDATA is that I have some pretty good wiring diagrams/schematics.

I would really like to have working ABS.

 

Checking the wheel speed sensor coil resistance tells you that the coil is still intact, but does not tell you whether the information being sent to the ABS control module is appropriate. You need to measure the mV-AC output from the sensor to make sure that it is in the range of 200-350 mV-AC output as stated in THIS helpful Tech Article. Too much airgap between the sensor and the reluctor ring in the wheel bearing assembly can cause an erratic signal code. This is the condition discussed in the Tech Article linked to above.

An open circuit code could be caused by a fault in the wiring either at the sensor itself or between the sensor harness connector and the ABS control module. Testing the resistance of all involved wiring would tell that tale, however you may want to move the harness around as you run the test to see if there isn't a broken wire that sometimes makes contact and sometimes does not.

 

Given the condition of my Blazer it appears the vehicle was garage kept most of its life. Upon changing the drivers wheel sensor there was only a slight surface rust around the hub and no rust under the mounting surface of the wheel sensor. I will try the test with the millivolt readings to determine the output.

 

I have seen new, out of the box aftermarket wheel hubs with out of spec WSS voltage that needed to be filed down to get it back into the proper range.