I have absolutely NO IDEA wth happened! I was so freaking careful with it (I took the ABS module out to ensure it stayed safe). I thought the most dangerous thing in doing it was the risk of crossthreading the ABS on assembly. I'm waiting on replies from EBCM repair companies right now to see if they can take a look at it as I still can't find any wiring issue.

 

have you checked the module for cold solder joints on the board? its very common on GM ABS modules. you can also try cleaning up the board if it has corrosion.

 

Maybe get another sensor just for testing, cheapest will do, no need fit it, it's only there as a "load". Think of it as insurance, worst case scenario is you're left with a spare sensor, cheaper than an ECBM repair.

Again double check at the ECBM connector, make sure you can measure the sensor load, I'm sure the last thing you need is to remove the ECBM unnecessarily. If you can see the sensor, the that will confirm a module issue.

With all the care in the world, moving/disturbing any complex part cab be a risk, just removing connectors can cause a flaky solder joint to fail, so bronxteck's advice is sound. If you do remove the ECBM, take a close-up pics of the pcb connector pins (solder side) I'd be happy to comment (electronics is my life's work, not gonna say how long)

You're right about cross-threading, screwing in the glands can be very tedious, SS can be difficult to seal.

 

Just wanted to give an update. I was getting 5390 ohms on the right rear wheel sensor (working). On the left, it was 5350 ohms.

I still couldn't figure anything out or find a wiring issue. I ended up removing the EBCM and sending it out for repair. I wasn't comfortable opening it up myself. Unfortunately, he said he could not detect any problem with the jumpers. He had this to say:

"If you have definitely ruled out the sensor, the ring, the wiring, and the harness (frayed wires are common), then the only other possibility is a bad processor inside the module. The problem was NOT a broken jumper inside the module, which is common and fixable. All your jumpers were good. Processor failures are not repairable though and can only be diagnosed through a process of elimination."

This brake project has turned into a nightmare. I've gone through everything for the quadruple check while the module was being shipped off, and I get the same ohms measuring directly at the EBCM harness as I do off the wheel speed sensor. I don't understand how I killed my processor during this job, but it doesn't look good.

 

Just wanted to give another update. My issue has not been solved, though I am experiencing much more electrical issues than just a single wheel speed sensor error now. I am trying to source a replacement ABS module to try.

In the mean time, I took it for a 35 mile drive while connected to the Tech 2. I had correct wheel speed out of both front wheels and both rear wheels were 0, though the only DTC was the C0045. About 3 miles prior to the end, I received a SERVICE BRAKE SYSTEM ERROR. I pulled over and checked codes and was receiving a C0041 (Right Front/Performance Issue) along with the C0045 and then the C0050.

Another mile down the road, everything went haywire. Gauges were all over the place, shooting down and then all the way up and flashing...fuel, oil pressure, speed, all of it.... Service Brake System, Service 4WD, Check Charging System, Rear Air Suspension...everything that exists, as well as the gauge cluster backlights turning on and off quickly. I made it home....nothing was effected with the engine performance.

Upon recranking, I can't get the gauge cluster to go erratic again. But, the C0041, C0045, C0050 are now constant errors. The only working wheel speed is the front left. The front right wheel will register speed only up to 4MPH. After 4MPH, it just continuously says 4MPH on Tech2. I got a replacement wheel speed sensor to try and the replacement will not register over 4MPH either.

All wheel speed sensors ohm out correctly, have proper continuity, and can't detect any short to ground.

I am going to clean my body grounds again. I also just replaced the battery in case it had some phantom issue. I've checked my alternator and the voltages appear correct. While some of the conduit of the main wire harness that runs along the driver side frame is cracked/dry rotted?, I can't find any type of wire damage.

No point in posting more DTC's as it's just tons of loss of communication codes. I bought a subscription to GM Service Information to download documents, but haven't really found anything useful yet.

Going to keep at it and see if I can figure out anything before I have to send it off somewhere to be looked at.

 

And yet, another update:

I sourced a replacement ABS module from a 2006 (I have a 2007). I got it connected today. The ABS and traction control dash lights are now out. Though, I don't know how it will do in motion. I haven't taken it for a drive to see what it will do as I can't now....

I manually bled prior to ABS bleeding. Brakes stiffened up to what I would call normal. Following, during the ABS bleed using Tech2, everything felt perfectly normal (as I have done the ABS bleed before in the past and know what to expect). However, during the rear right wheel and before the rear left wheel, my peddle stiffness turned into nothing....completely gone. It was nice and firm at the beginning of the rear right wheel and by the end, it was non existent. I still moved on to the rear left....and it went through the normal procedure but when it kicked the ABS pump on, it didn't take out much fluid at all like it did for the other wheels.

I swear I'm not THAT incompetent. This whole thing has been one step forward and ten steps back.

Any ideas on this brake pedal symptom? I can detect no leak from anywhere. Though, it's dark and I have given up as it is 12:30AM and have had enough today. Could my master cylinder have given out during the ABS bleed, causing my pedal issue? Could this be a hydroboost issue?

 

No doubt in the light of a new day you'll resolve the problem. Think it would be very unlucky for a hydro-boost issue to have suddenly developed, so let's assume for the moment it's OK.

BTW I am no expert on brake systems and there are more experienced members on the forum who could offer better advice, however I have done the exact same job i.e. replaced ALL the lines and hoses, removed and serviced the ABS Module, Brake Reservoir etc and bled the system with a Tech2.

I'm also aware it can be a very lonely place when you're stuck with a Hummer, especially here in the UK where there are very few no GM service centers, so I'll try and be as supportive and helpful as I can.

Assuming there are no other problems, the hydro-boost is OK, there's no leaks, then it suggests there is still air trapped in the system. Note you may have bled systems before, but perhaps not after changing all the lines and completely draining the entire system of fluid, so this scenario may well be different.

Researching at the time I found this note :-

• The master cylinder should be primed by loosening MC1 and MC2 one at a time and pressing the brake pedal until fluid starts to leak out. Unlock the fitting on brake “pedal press” and lock again on brake “pedal release”, wait 15s between cycles. Keep going until no more air seeps out the system. Take care to capture any surplus fluid using rags or cloths placed underneath the MC1 and MC2 glands. When finished make sure MC1 and MC2 lines are fully tightened.

Perhaps trapped air at the master cylinders is "mimicking" a hydro-boost issue?

A while back I got called to a Hummer with a similar problem as yours, the owner said absolutely "no leaks" and was also worried about the hydro-boost, however it turned out there was a leak, the fluid was filling the engine skid plate i.e. out of sight. My point is this tiny leak had a massive effect, so it might be worth double-checking for leaks, especially above the ABS Module where the joints are hidden from view, everything should be bone dry.

It might be worth re-doing the procedure and manually bleed as you did previously, if you can get back to that same point it would be good, then retry the auto bleed.

Hopefully you'll get there 🤞

 

These types of issues can be and are frustrating, I fought a 2006 Denali I owned for a while before finally stumbling on the cause of an issue very close to yours.

The truck kept a C0045 most of the time and would go to limp mode randomly or just go crazy like yours did, gauges would blink, sweep just random stuff along with a bunch of U codes, loss of communications.

But not to be stumped by this I continued to troubleshoot and finally found a bare wire on the front left wheel speed sensor cable that just at the correct angle would ground to the wheel. The prior owner had at some point changed the wheel speed sensor but had not correctly mounted the retainer in the bracket and allowed the speed sensor cable to rub on the wheel when turned just right.

What does the live data show when driving the truck for all the wheel speed sensors, do all live streams look ok?

I see where you ohmed the wires all the way back to the EBCM and they ohmed good so that should prove the wiring back to there.

I see where you sourced another EBCM but the issues continue, can you validate that the EBCM is without issues of its own, was it proven prior to the purchase.

I don't see where you commented about the live data stream, I may have missed it but if the C0045 is current then the live data stream should show it?

Neal

 

Last and final update....

SUCCESS! I'm not sure what I did wrong in the original bleeding, but after starting over, I got a lot more air out of the master cylinder. Moved on to the rest of the wheels manually. And then redid the ABS bleed. All is well. I took it for a decent length drive over 25mph, all wheel speed sensors are recording correctly, and my brakes feel great.

I really didn't want to acknowledge a hardware failure....I was still thinking it was something that I messed up with the wiring. But, it does appear it was my EBCM and it seems I'm finally done with this project. It took a 9 hour round trip to source and wasn't cheap but I got it considerably cheaper than buying one off of eBay.

For future memo, changing the EBCM does NOT require new programming, at least not on a 2007. This is confirmed in the GM service information I subscribed to for a few days. Seems people on other forums (and sellers on Ebay) think this has to be programmed. But it doesn't.

Thank you to all who chimed in with info and things to try! On to the next project!

 

Glad you got there....well done!