Bad brakes on gmc suburban, replaced master cylinder,rear wheel cylinder and abs control module,bled system,still have spongy brakes and ABS come on right before it gets stopped.

Jesse, The module will not stop fluid to rear brakes, a bad master cylinder will,leaking lines, air in brake system, faulty metering block if equipped, collapsed flex lines or pinched brake line faulty caliper or brake cylinders,etc. will cause the possible feeling of no rear brakes.
(ABS Module components) the ABS speed sensors and the ABS control module . When the brake is applied, the ABS control module reads the speed data from the speed sensor and sends the correct pressure to each wheel to prevent any wheel lock up, eg. sliding/skidding Links below have more info.
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Service Stability System AND abs Pump issue

ABS Control Module Replacement Service Cost YourMechanic

https://www.rockauto.com/en/catalog/cadillac,2002,escalade,5.3l+v8,1431695,brake/wheel+hub,abs+control+module,1844

possibly a faulty caliper

try bleeding your ABS block first, if that doesn not work could need a master or proportioning vavle. Some scan tools are capable of bleeding the ABS system on some vehicles, and some you have to bleed manually.

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.

blead from the furthest point forward... so , if your master is on the firewall on the drivers side.. rear right , rear left , right front and then left front...

ANTI-LOCK BRAKE SYSTEM (and HCU-Hydraulic Control Unit)
General Information The 4-Wheel Anti-lock Brake System (ABS) is an electronically operated, all wheel brake control system. Major components include the power brake booster, master cylinder, the wheel speed sensors, and the Hydraulic Control Unit (HCU) which contains the control module, a relay, and the pressure control valves. The system is designed to ****** wheel lockup during periods of high wheel slip when braking. Retarding wheel lockup is accomplished by modulating fluid pressure to the wheel brake units. When the control module detects a variation in voltage across the wheel speed sensors, the ABS is activated. The control module opens and closes various valves located inside the HCU. These valves, called dump and isolation valves, modulate the hydraulic pressure to the wheels by applying and venting the pressure to the brake fluid circuits. Some models are equipped with a Traction Assist (TA) system. The TA system senses wheel spin upon acceleration, turns on the Hydraulic Control Unit (HCU) pump and applies fluid pressure to the appropriate rear wheel. Two additional isolation valves in the HCU will also close to permit fluid to flow only to the rear wheels. The TA system monitors TA usage to avoid overheating the rear brakes. If the system does sense brake overheating, the ABS module will inhibit TA operation until the rear brakes are permitted to cool down.
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SYSTEM COMPONENTS The anti-lock brake system consists of the following components:

• Vacuum booster and master cylinder assembly
• Hydraulic Control Unit (HCU)
• ABS module
• Wheel sensors
• Pedal travel switch

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On 1992-1994 and 1995-00 a scanner is used to perform the brake bleed. But on yours, I think it's different according to the manual.
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What do you mean change the cal. on the rear also? Do you mean Caliper?

did you bench bled master? if yes do you have abs system,if so you must bleed at abs block,if it has bleeders, if not then you must line bleed all 6 lines.2in from master 4 out to wheeles. then rebleed wheel in cylinder.If you have bleeders at abs block you dont to rebleed wheels. best dun with powerbleeder. hoooooops this helps

Hi, you are experiencing the GM brake pedal, this is a common problem, most of the time the abs module is to blame. if air gets trapped in the module it will always be spongy. you need to crack the bleeders just after the abs unit and have an assistant push down on the pedal and do a "non-pressure" bleed on this to get the air out. then bleed the whole system all over again. good luck and buy brake fluid in bulk. I went through 3 big bottles before i got all the air out.

Yes master cylinder and maybe ABS sending unit. Also is there a sound of an air leak it may also be your brake booster

Did you adjust the rear shoes out? If the rear drum brakes are out of adjustment they will give you a lot of pedal travel. If the pads are worn have no fear of that U-CLIP brake spring, just change one shoe at a time. Take the spring off one side, change the shoe, put the spring back on the post and do the same to the other shoe, no problem.