2002 GMC Sierra Ext. Cab w/4.8 P0442

Bleeding brakes on this truck but as soon as as I start it, pedal goes to the floor. Try to ABS Bleed with my scan tool, it tells me to correct the codes that are set. I've reset the computer but it retains the codes for the "Low Speed ABS Activation". C0221,C0222,C0225 and C0226.

While trying to ABS Bleed my scan tool asks my transmission and on next screen it asks about throttle type. Where would I get that information from? My owners manual is missing pages. My Thinkscan Max says my truck is equipped with 4wal 3 sensor and VSES.

What options does it give you for throttle type? I think they're asking if it has an electronic throttle, or a throttle cable. You'll be able to tell easily by looking at the throttle body itself. Or the accelerator pedal.

C0221 and C0225 are circuit codes and will set KOEO. As you found, the EBCM won't let you run the automated bleed procedure with current faults set. If you're dead set on doing the automated bleed, you could try installing some resistors across the wheel speed sensor connectors and clearing the codes. Service info the sensors should be between 700-10,000 ohms. The actual resistance is probably closer to 1,500-ish.

Gotta say, though, I don't think I've ever fixed a low brake pedal by doing the ABS bleed. Sounds backwards, but I've never found it makes a difference to pedal feel/travel. Maybe others will chime in. Anyway, what I'm trying to say is, if the low pedal is your biggest concern, then I'd put the ABS bleed aside and revisit the base mechanical/hydraulic system.

I thought I'd cleared the codes, but I'd cleared the Powertrain codes. I finally figured that I had to go into the ABS section to clear those codes. I didn't mention my fix for low speed ABS activaton. I pulled the sensors and sanded the mounting surfaces and the shims to get rid of the rust. Then I painted the mounting surfaces with rust repellant hoping that fixes the issue.
The ABS Bleed is because I found rusty lines and the back brakes had one pad on each side completely worn down and the other side almost new. Back calipers were rusty and I couldn't compress them so I replaced them. I also found contamination in the reservoir. I did all that so that I don't have to tear it all apart in the near future.
Sorry it was so long winded.

The 2 options are without throttle actuator control sensor, or with sensor. I've done some research on this and now know where to look from the module.

W/throttle actuator control = electronic throttle body
W/O = throttle cable.
I also have never had any improvement in pedal feel after using the automated bleed. Usually if the pedal still sucks after a normal bleed procedure, I'll bleed the master cylinder by just cracking the lines one at a time with someone in the truck to run the pedal. Then bleed the 4 corners again starting as far from the master as possible (RR, LR, RF, LF), then maybe once or twice with it running.
I've come to realize that pedal feel is subjective. No two people seem to feel the brake pedal the same way in my experience working with other techs.
Maybe take it for a drive and see how you feel about it when you get back.

Found TAC module, purged the brake system by ABS Bleed and running motor while bleeding brakes. I now know why you and Tyler think ABS Bleed is pointless. The bubbles I got on motor running bleed after ABS Bleed proved to me I wasted my time with ABS Bleed.
Update on truck is no low speed ABS activaton and brakes work fine. Now have to figure out what is causing my wipers to only work on high and won't reset to home when shut off.

ABS issue has been resolved, thank you Tyler and Noah for your suggestions.

Brake lines have been replaced,  system has been bled but pedal isn't as responsive as I would like it to be. Will address that at later point, had my son pumping the brake while I cracked the bleeder screws. I now have a P0442 code, checked gas cap seal along with sanding surface rust on filler tube near gas cap seat. When filling tank I could smell gas after I started pumping gas, I also could smell gasoline when I had to remove charcoal canister when installing rear brake line.  My 2 scanners don't have that bidirectional capability, is there another way to test the EVAP system without a scanner? 

Your best bet may be a smoke machine. I don't love the smoke machine options on Amazon, but something like this would at least get smoke into the system for visual inspection:

www.amazon.com/AUTOOL-Automotive-Detecto...tible/dp/B0BGB41DLK/

The flow gauge may or may not be accurate based on past experience with this brand.

With the smoke machine, you'll still need some way to seal the vent. You could find the vent valve and find a way to physically cap it, but that'll take time and effort. And, it won't tell you if the vent valve itself is the problem, which is a good possibility on this YMM of truck.

I know from experience that the TopDon TopScan will run bidirectional EVAP controls on that YMM of truck. Other similar tools from Kingbolen/Launch/Xtool will probably do the same:

www.aeswave.com/TopScan-Pro-p10478.html

You can also use the EVAP Purge/Seal function to verify that the purge valve is opening/closing as it should.