Guys, I finally figured out a way to bleed the ABS block via forscan. This helped the pedal feel and clamping force a lot. I have done many "ABS service bleeds" and did not get this good of results. In forscan on the "read pid data" select the ABS pid group and then also choose the "control" function add the ABSLF_I ABSLF_O ABSRF_I ABSRF_O
Click on the "play" button then click on the "control" button on all 4 of PIDs will show "enable" "disable" now with your foot on the brake click "enable" on all 4 valves then click disable then release the brake pedal. This will allow fluid to flow through the ABS block so treat it like a normal brake bleeding. Apply brake pedal and hold it, open the valves then close the valves. Repeat this until the the brake pedal no longer drops towards the floor/firewall. I had a lot of air in my ABS block so I did this process 5 or 6 times and now when I hit the brake pedal I can now hear the tires chirp to a stop. Hope this helps you all out.

 

This helped me, thanks.

I think Forscan has changed a little since this post; I had a little trouble sorting out the setup but these instructions were key to getting there.

What tripped me up was finding the "controls". In Forscan 2.3.65 after I added the ABS valves as "control" types and closed that dialog, I pressed "Play" but couldn't figure out how to get the actual on/off buttons to show up. Finally I realized that the button I needed was greyed-out AND had an X through it -- geez. I know programmers aren't always geniuses when it comes to user-interfaces, but come on man! That's just wrong.

I did as described above: brake on, valves open, valves close, brake off. I never heard the valves operating. I also tried feeling for them with my hand on the module while someone else clicked the button, no feedback there, either. I'm not totally sure that I had air in my ABS, so this may not have even been the right fix for my problem (pedal was not soft but when ABS came on I would hear the motor but not feel anything in the pedal). So all my above is just a recounting of my experience, in case it helps inform someone else's.

Attached some Forscan screenshots in case it helps someone else.

 

First time poster here, I've read a lot of threads over the years and found them very helpful so thanks to all of you who frequent these places. I'll get right to the point.

I have an early 99 cclwb 4wd with 2 wheel abs. I recently replaced the rear calipers and the master cylinder reservoir ran dry. OOPSIE.... I bled the brakes with the suction gun until no more bubbles came out and then some, The brakes work Ok but the pedal is a little spongy. I want to bleed the ABS unit so I have connected FORScan to it and it does not find the ABS module. I am using a OBDLink EX scan tool and the latest version of FORScan 2.3.70 and I hooked up the original PCM for testing, I thought maybe the 2001 PCM might be the problem but still no ABS module connection.. I have checked all of the fuses and the connectors at the abs module and it all looks good. I get the standard ABS dash light for a couple of seconds at startup which should mean the system is working OK.....?

Is there a better scan tool that would find the ABS? OR is it possible the ABS module is bad and still allowing the dash light to come on at startup?

MY other thought is this... there are only 4 wires that go into the ABS hydraulic unit... IF i knew what they all did I could hotwire it? any thoughts?

 

Update:

I'll share a hack that occurred to me while pondering this problem. What could dislodge air bubbles from the ABS unit? VIBRATION....
So, I grabbed the industrial strength corded unit from my wife's drawer that's usually used for other purposes and wedged that puppy up next to the ABS unit. I switched it on and proceeded to bleed the rear brakes.
Quite a bit more air came out and the brakes work better now.

Insert your jokes here............