Hello again everybody, its your local hummer dumbass who drives purists insane.

By popular demand, and for reasons related to the solid axle swap, I will be attempting to Hydroboost swap my 2008 and get rid of that God-awful electric brake system from hell that has no business being in a road legal vehicle. I will give the details on why the solid axle swap requires this in my SAS thread as well as go over alternative solutions.

As for non SAS related reasons here they are...
1. No brake pedal feedback - Fine for daily driving, but makes left foot braking while traversing obstacles offroad damn near impossible. You can't feel the "bite" point of the pads.
2. Inconsistent braking performance - IMO dangerous even for street driving - Sometimes the pedal is soft, sometimes it's hard, sometimes it stops quicker than others. No rhyme or reason. I've replaced every part in the brake system, there are no leaks, it just is that way.
3. Digressive brake performance - The pedal progressively gets mushier after a fresh bleed of the system. Usually takes about a month or 2 of normal driving before its noticeably softer. After towing, aggressive driving, or offroading, it becomes unsafe. However a quick abs bleed with a scan tool restores it.
4. Parts availability - Apparently I bought the last brake unit in existence off of rock auto a couple years ago, sooooo good luck everyone else. These are non-rebuildable(Allegedly but I think it can be done).

I want to expand on #3 here for a moment. There is 100% without a doubt a defect inside every brake unit where air is getting trapped somewhere in the hydraulic cylinder the pedal is connected to. I suspect that this is due to cavitation of the brake fluid somewhere in the unit that's getting into the pedal cylinder.
In these units, the pedal cylinder is used for nothing more than a glorified pressure sensor. Its full of fluid and when you press down on the pedal, a valve releases some fluid back to the reservoir and a sensor reads the pressure. The EBCM reads sensor voltage, does some math, and sends a dependent pwm signal to the pressure valves for the calipers. Basically... caliper fluid pressure(for rear) and caliper fluid volume(for front) is dependent on pedal cylinder pressure.
When air gets in here, less pressure can be created, the sensor voltage is lower, and you are left with less braking power. I have felt and seen on the scan tool up to a 50% reduction in pedal cylinder pressure at full pedal travel after wheeling trips or towing.

Anyway... Here's the plan. First of all. I have no idea what I'm doing and have no idea if it will work. I'll take one for the team in terms of experimentation.

Since I want to keep this factoryish with no lights on the dash, I'll need to have an ebcm for the rest of the truck to communicate with that will have the same functionalities as the oem one. I need to find an abs pump/module compatible with hi-speed gmlan(2007.5-2010) and with the same options as my truck. If you look at a 2008 Cadillac Escalade, you will find it shares the same gm hi-speed lan and rpo codes as the 2008 hummer h2. JH6(Hydraulic power disk brakes) and JL4(Stabilitrak). I will try to use that one. I found a used(hopefully good) one on ebay for $50. I am going to buy that just to see if it's even possible to program it to my vin and make sure the other modules accept it and don't keep looking for an ebcm that isn't there anymore.



Fun fact... The EBCM is such an important part of the can network that the vehicle wont even start with it removed. There are 4 total hi-speed lan wires on the ebcm. Two going in an two going out. Downstream of the ebcm is the Fuel Pump Control Module, the Air Suspension Module, and the Terminating Resistor. If there is an issue with any of these wires the network goes down and the truck becomes a very large paperweight. Here's the totally legally acquired wiring diagram of the network so you can see what I'm talking about...

If anyone needs (totally legally acquired) wiring diagrams for 08/09 lmk. I have a few.
Oh and here's for the EBCM. You're welcome.


I have the pinout for the Cadillac EBCM as well on my computer at home. If this works I'll upload it here.

I will keep everyone updated on progress. Might be a week or two.

 

Thanks for posting,
very interested in this one,

Neal

 

Gavin, as always a new path blazer and if anyone could pull this off its you! Getting rid of that Toyota created ABS unit will be a crowning achievement.

 

Do you ever sleep? I bet your brain is going 24 hrs a day. lol

I admire your tenacity and your skills. Will be waiting to see the progress.

 

I do not sleep. There is nothing else I am good at in my life other than this type of bull****. But at least kind of f-ing around will probably land me a solid job out of college.

I also feed off of people telling me not to do stuff. I recently posted about my brake issue and possible solutions on the carhacking subreddit. I had a few people there tell me “buy the correct parts”(lol what parts?) “you shouldn’t be doing this” “it’ll never work” and my personal favorite… “you’re going to kill a family of 7 in a minivan.” No I’m not.


Everyone: “That’ll never work”
POV: me when it does…


Forgive my rant I’ve legitimately been awake since 6am… yesterday.

 

**********UPDATE**********
Hello again...

I have a very important update that everyone(especially me) will be very pleased about. I have confirmed that an abs pump and ebcm from a 2008 Cadillac Escalade(P/N 15834127) is a direct fit to the 2008 hummer h2. And by "direct fit" I mean not at all, BUT the electronics with little effort other than changing the connector. I didn't even have to program it, and all of the modules in the vehicle are happy. No codes from anywhere. Only codes I have are 6 codes all for sensors not being hooked up. It was as simple as matching colors. Minimum required was the two powers and grounds, 4 hi spd data lines, and the serial data enable wire. Here are the confirmed correct pinouts for each module. They are oriented looking at the front of the connector on the harness side. Be careful as orientation is quite confusing on these.



Thanks to the free charm.li website for somehow having the escalades diagrams that alldata didn't have.

One weird thing I ran into is the Escalade EBCM has a set of tan data wires and a set of yellow data wires while both pairs on the Hummer EBCM are tan pairs. The solid colors are can- and the striped are can+. I don't think it matters which pair connects to which pair as long as you don't cross the pairs and you connect + to + and - to -. Even though both pairs are tan/tan-black on the hummer side, they are still next to each other. The hummer side pairs are adjacent long-ways on the connector while the Escalade pairs are adjacent short-ways on the connector(vertical). Can stuff is pretty forgiving as long as you don't put 12v to it, its all 1 voltish, so if you screw it up, you probably wont break anything, it just wont work. The way you know it works is by testing resistance with a multimeter between can+ and can- on either pair. It should be 60ish ohms. If you did it wrong, it will say 120 ohms(only one side connected correctly), OL(multiple bad connections), or 0 ohms(just give up if it says this).

That was the big headache out of the way... Now I have to order parts: Master, booster, hydraulic hoses, and brake line.

Wish me luck!

 

That's great news, if you need any help finding anything post here and we'll lend a hand,

Keep us updated,

Neal