Brakes need to be bled

To my knowledge, the porportioning valve can't be bled using the ABS bleed feature of a scan tool and has to be manually bled.

The brakes will need to be bled normally, and GM has a depressor tool specifically made to be installed on the valve while bleeding the brakes: J-39177.

You'll have to bleed the front and rear brakes as normal, but with the tool installed in order to remove the air trapped in the valve.

If the master cylinder is replaced, care must be taken to prime the new master cylinder by removing all of the air and completely filling it with brake fluid. The spongy feeling is air that is still in the circuits. You will need to bleed the back brakes as well as the front ones again. The order that you bled them seems correct, but perhaps there remained some air in the main trunk lines.

For the best results 2 people are needed. Start at the further distance wheel cylinder and bleed at least three (3) master cylinder reservoir volumes of fluid (back brakes). Bleed the fluid with use of a piece of tubing attached to the bleed port that is long enough to reach almost to the bottom of a long neck or tall clear jar (clear drink bottle works well). When the bleeding begins, after one or two brake pedal pushes, make sure that the end of the tubing is below the surface of the fluid and keep it under. It best to have a clear bleed line (to observe air). Keep pumping the brake pedal while being careful to not completely empty the master cylinder reservoir (leave 1/4 full always). Repeat the same technique for each wheel cylinder with at least two (2) reservoirs full for front brakes. Partially close the bleed ports when almost finished (at least 5 pedal strokes without exit of any air). Completely close the ports during the down stroke of the brake pedal, with the tubing still attached. Be sure each bleed port is closed snuggly.
Most of the brake fluid can be reused, but not the darker portion at the bottom of the jar.

sounds like a master cylinder issue.

When you do that, you must bleed the whole system in a sequence order. You start with the brake line that is the longest and bleed that and then move to the next and so on. So you should have bled RR, LR RF and LF brake lines in that order.

Abs brakes have to be bled in the order the manual states, you will need a power bleeder then follow instructions in the manual. it is the abs cylinder that is hard to get the air out of, imposable if the instructions are not followed .

if you didn't bleed master before bleeding whole system you may still have air in system, in which order did you the bleed brakes?

If you have a manual for your vehicle, check how to bleed the system. Certain vehicles need to be bled in a certain order of sequence. If you are using a one man bleeding kit, when you don't see air bubbles in the clear tube but see only fluid, then it is bled properly.

on the back side of calipers you will see a small bleed fitting -- attach a small 1/4 inch CLEAR hose to this fitting and run it into a catch bottle ( of some kind ). top off the brake fluid reservoir with fluid. now you will need a helper to sit in the drivers seat and ready your commands. use a small wrench and turn the bleed fitting counter-clockwise ( only about 1/2 turn ) -- have your helper press down the brake pedal and hold it to the floor,, and with the brake pedal to the floor you need to close the bleeder,, as soon as it is closed - have your helper let up off the brake pedal,, now open the bleeder again and have them push and hold the pedal to the floor again,, close the bleeder -- have them release the pedal,,, continue this process until you see no air bubbles flowing out the bleeder ( thru the clear hose ). keep the reservoir topped off with fresh brake fluid ( do not let it run dry or you will have to bleed the lines again ). repeat these steps for all calipers on the car and you will be good to go. --- also keep in mind that as soon as all the air is bled from the system -- when you pump the brakes, the pedal should get very hard and stiff,, if it goes to the floor after you have bled the system - then you still have air in one of the lines and you will need to continue bleeding.

c...

JEEP VECHICLES 2001 MODELS AND UP HAS TO BE BLED USING A DRB BLEED TOOL.YOU HAVE TOW VECHICLE IN.MOST TIME YOU CAN TRY MANUAL BLEEDING BUT BRAKES WILL BE SPONGY AND ABS LIGHTS WILL TURN ON.THE DEALERSHIP HAS TO BLEED IN ORDER TO GET GOOD SOLID BRAKES AGAIN.

It won't make any difference. The trick is to attach a piece of hose on the bleeder screw. Vacuum line or something small that will fit tightly over it. Loosen the screw, attach the hose. Put the other end of the hose in a clear glass or plastic bottle about half full of brake fluid. Then pump your brakes until no more bubbles come out of the hose. Have someone hold the brake pedal down, and tighten the screw. Repeat on all 4 wheels.