Hi everyone, I'm hoping someone can help me figure out what's going on with my car.

Background: 2010 Corvette Grand Sport 6-speed, 102k miles
Related Mods: Goodrich Steel Braided Brake Lines, AFX 2-piece rotors front and back, Carbotech 1521 pads front & back, Motul RBF600 fluid

My car's ABS system no longer works. When I panic brake, one of the tires (usually the rear) just locks up and drags across the ground. I can do this to the point that it kills the engine if I don't put the clutch in. Nada. We hooked up a computer to the car and replicated the phenomenon while monitoring and watched all the wheel speed sensors function correctly and register the wheel locking up. The EBCM is powered and registering activation, the "ABS Active" light comes onto the dash, and there are no error lights at all. The car thinks it's working perfectly, except it's totally not.

Here's where it gets really weird, if I accelerate hard up to 80mph or so, then touch the brakes AT ALL the "ABS Active" light comes on and I'm locked out the brakes entirely.

I assumed that it must be that the EBCM had gone bad so I bought one on ebay, watched the youtube video on how to replace it, and executed the job. The problem was that the used part couldn't hold a seal when we screwed in the lines from the master cylinder. We tried everything, up to and including re-flaring the line ends. Still leaked. I ended up putting the original part back in the car just to get it driveable while I figure out my next move.

RIght now I'm planning to buy a brand new EBCM from gmparts house, and probably new brakes lines from the master cylinder to the EBCM just to be sure. This is going to cost about $1500 though in parts, so before I drop that much money I want to test the forum waters in the hopes that one of you gods can point me in a better direction, or at least give me a warm fuzzy that I'm doing the right thing.

Here are the parts I'm looking at buying:

Control Module: 25994201
Modulator Valve: 25994202

I can't find part numbers for the MC - EBCM brake lines right now, but I'm planning to either replace them or have somebody fab some up if they leak with the new EBCM module.

If you folks could lend some insight it would be much appreciated!

Chris

P.S. For some dumb reason I went to my dealer's mechanic. I had expected inadequacy going in and I was not let down. They told me it was because my rear tires had low tread! This is the part where you insert the laughing scene from goodfellas...

 

Look for a member on here by the name Dano523 he is the man on all things corvette. Good luck.

 

This sentence seems to have gotten a little garbled.

Do you mean that

1. you're "locked out [of] the brakes entirely" i.e. you have no braking at all, or

2. you've "locked [up] the brakes entirely" meaning all four tires are skidding?

 

Thanks for the tip, I'll reach out!

What I mean is that after sustained hard acceleration, if I go to step on the brakes, as soon as I apply brakes the ABS pump activates for a brief period. After a second or two I have my brakes back and can slow down. Still no ABS though.

 

If the car is not throwing codes, then not on the electronic side of the math being the problem.

Chances are the top of valves and inside of the solinoids channels are covered in grim/rush and just need to clean them.

On used ABS units, always, and I mean always, pull the electronic cover play off and check the top of valves and inside of the solenoids for debris.

Inside the solenoids are easy to clean up with contact cleaner and give them a shot of silicone so the vavle will glide through them without problems, while on the valves, may have to break out the scotch-brite pads instead.

Pretty good photo of the what the top of vavles look like on some used ABS units, and cause problem with the vavles not cycling correctly as needed.


And the inside of the solenoids from the above unit that they just need a quick clean and a good shot of silicone to make then right as rain so the cleaned vavles don't stick in the bodies.



As for when you go to put the electronics top piece back on, use a touch of RVT to help the gasket part seal off correctly.

The electronics top/cover removes from the body via the 4 Torques screws that hold is on.



Also just a FYI, but before you put the electronics back on, good idea to back blow the system out (both ways) in case there is crap in the lower channels. I will cycle the pump as well, so it can flush it self out before using the used EBCM as well.

Lastly, need the rim and tire size on the car, since may be just enough out of wack at higher speeds to cause problems. Normally the car will throw AH Codes when the tire ratios are off, but may be just at the edge with off ball tire size that is only a high speed problem isntead.

Also, need to get a tech II scanner on the car to really check for codes at the body/EBCM level. Normal code readers will not get this deep in to the needed levels that the codes may be located.

 

It may be as simple as air in the ABS lines. This will take a Scan Tool (AKA "Tech 2"). But the chinese ones won't work on later models reliably, I had one and tried to flush my brakes on my '11 GS, but no luck with the chi-knockoff T2's

so a dealer trip or to a shop with a bi-directional scanner may have to flush the ABS. If you break the system, again will need a flush

 

Clone tech II/GM nano works fine.

Just have the car is ACC mode, not Run mode/motor off, and you can use the automated brake procedure on each caliper to cycle the pump and valves to get the air out of the ABS unit. If you try to do this with the car in run mode/motor off, then ABS pump will time out since it trying to do two things as once instead (monitor the tires, and run the pump as well).

As for final bleed of the calipers, although the tool will walk you through the process at each caliper for the most part, before moving on to the next caliper, do a quick brake pedal pump up for about 6 strokes with the bleed valve closed, then as you hold the pedal down, have someone slightly break the bleed valve open and close it again before you end up with the pedal to the floor. This manual pedal pump up over/above the tool procedure of just using the abs pump will break free any air bubbles on the seal/inner surfaces that the automated brake procedure may miss when it just using the pump to push the air out with the caliper seals sitting still instead.

 

As stated above Tech2 clone will work fine.Have a battery charger on while flushing EBCM