Pontiac Repair: No rear brakes, rf sensor, rear brakes

Question
QUESTION: My son has a 1999 Pontiac Grand Am with a 4cyl. The traction control light and the ABS light comes on and off. I put on both front rotors, both front calipers and pads, I also put on rear shoes, did not turn or replace the drums. I also put on a master cylinder. The rear brakes only apply a little - front brakes locked and you can still turn the drums. We brought it in to read the codes and it came up with these, C1222, C1225, C1226, C1233, C1236, C1262, C1257, C1265, C1276 & C1278. Basicly telling me that the RF wheel sensor / harness is bad. My question is could the RF sensor keep the back brakes from working? Is there a porposionating valve that could be stuck in the front only position? I bled the brakes completely. This problem was there before I replaced anything, however it did stop better before I replaced the parts. Please let me know what could be the problem. I am more interested in getting the rear brakes working more then fixing the ABS.
Thank You.

ANSWER: Hi
I really doubt the front WSS could cause these problems.
There is a proporting valve, it is located as part of the ABS modulator valve assy. It IS replaceable, but it looks as if it is a pretty big job.
Are the rear braked adjusted properly?
Do the emergancy brakes work(Hold the car?)
If not I would check adjustment. There should be a slight drag on brakes when rotating drums on axles. Very slight.
They should NOT turn free and easy, slight drag.
Please follow post back, if needed
I Hope this helps.
Pawl

---------- FOLLOW-UP ----------

QUESTION: There is a slight drag. I didn't check the emergency brake to see if it held the car. I will try that. But I don't think that is the problem. I believe the rear brakes are installed correctly and also adjusted correctly. From what you have said, you think it could be the ABS modulator valve assy.? If so I could pick one up at the bone yard. I used to be a mechanic but I changed professions 4 years after ABS was introduced. So I have no real experience working on it.

Answer
Hi
Yea, good move to change professions!!! lol.
I would advice a boneyard....make sure they give you some sort of warranty, if avalible. Of course you know that.
After you acquire it, follow back I'll shoot the bleed procedures, not too diffucult.
If avalible, you can speed up the bleed process if you can or borrow a scan tool to automatic bleed the valves. Not totally necessary though.
I'll await your follow...
Pawl