1994 Pontiac Grand Am 6cyl. The rear brakes are locking up under light pressure. Checked both rear wheel cylinders and are fine. Emergency Brake not sticking. Brakes are not too tight. No breaks in the line. They were working fine no brake work was done, they just started out of the blue.

left front wheel sensor is not reading replace wheel speed sensor

What order did you replace the items in

I've had the same problem before, ended up being a bad master cylinder that I just purchased. Replaced it with a different brand and it worked fine.

Have you checked the emergency brake ? The cable could be locked up. Slowly apply e brake if it feels loose the cable is locked up. You could also have someone watch the cable near the rear wheel to see if it moves .

you may have a bad ABS module but you may need further diagnostics to confirm this

The parking brake problem could have started the problem you are having in the coldest weather. Some may disagree but look carefully at the emergency cable parts. The cable is suppose to equalize the pressure to each wheel. Some of the rear brakes are made to automatically adjust the SERVICE brakes when you use the emergency brakes. Therefore if the emergency brakes are not automatically tightening the SERVICE brakes, you can get excessive play in the "star" wheel and the flat rod that spans both shoes.

This means that the brake cylinder pistons can travel
too far in the cylinder and are trying to bridge the gap. The hold-down pins and springs are loose too.

You can also have moisture in the rear brake lines and the "Brake warning light" is coming on because the proportioning valve is not returning to center in the lines. You should have a power bleed job with a cleaner run through the system and new fluid. That may fix the problem without checking the adjustment of the rear brakes.

The emergency brake light is also the low brake fluid warning light. Check the level in the reservoir. As the brake pads wear the fluid will drop, so if the brake fluid is low, check the pads to make sure the lining material is thick enough. If you have drums in the rear, check the wheel cylinders to make sure they aren't leaking. If everything checks out ok just add a little fluid to the reservoir and that should take care of the light.

It could be a proportioning valve, and there's also the chance that the portion of the master cylinder that operates the front brakes is going bad. Have you had a pressure check done on the front brake system? Also, some vehicles have a variable proportioning valve, so that when the vehicle is loaded, it allows more pressure to the rear brakes. These can sometimes stick in place, causing the fault that you describe. Hope this helps you out.

Make sure there is nothing leaking onto the brake shoes. Also, make sure that the emergency brake is dis-engaging and the cable isn't hanging up. If the original wheel cylinder had been leaking, the brakes may need to be replaced if they were contaminated. Also check that the drum itself is round. If not, the shoes will lock the wheel when they are on the high spot. An easy "backyard" way of checking the drum is to move it to the other side. If the problem moves to that side the drum is out of round.

What happens is the brake cables rust inside the cable sheath and then they won't slide easily. There's no good fix for this other than replacement. It's not easy to even find where they are stuck.It might be possible to find the end of the cables at the back wheels and pull the cables back---to release the tension