OVERULD

I am posting this for a friend who owns a 1996 C4. He says that every time he starts the car and backs up, with his foot on the brake pedal he will feel the ABS system kick-in and the pedal will pulsate then move towards the floor. This happens in the span of about a car length and a half as he backs up. Then the system functions normally as he drives and the car stops normally.

The car has 40,000 miles on it. He has been told that it needs a new EBCM but is not able to find a new one through his normal GM parts sources.

Has anyone experienced this same symptom and if so, what finally resolved it? Also, any recommended sources for new or aftermarket ECBM ABS modules?

Attached photo is of the RPO codes decal from his car if that is helpful.


Thanks,

BJ

SJW

ABS parts for older Corvettes are starting to vanish from the market. Supply is dwindling. I'd probably start with Chevy dealers, then move to E-bay, NAPA, etc.

Having said that, are you sure the system actually has a fault? Is it possible that what he's experiencing is just the normal self-test cycle that the ABS system goes through every time the car begins to move after a start-up? If he's a relatively new owner of the car, he might be worried about something that's normal vehicle behavior. Is the ABS fault warning lamp illuminated in the DIC?

Live well,

SJW

bac22

The 96 has and OBD2 interface should scan for codes first to see if the EBCM is throwing anything or you can pull the codes manually http://tech.corvettecentral.com/2011...trouble-codes/.

Does the system work when driving normal forward and then slamming on the brakes to make ABS kick on? If the answer is yes I question the need for a new EBCM.

I assume the basics have been done? Flush and fill brake fluid? Master brake cylinder is full to proper levels? Rotors/pads confirmed to be at recommended minimum specifications?

I would suspect a wheel sensor going bad more then the EBCM. There is a self test that it runs for about 10 seconds on start up. Ask your friend to wait 30 seconds after start and see if the problem stills occurs.

And lastly is he backing up on a hill with gravel? That would cause it to kick in too. Or does it happen no matter where he backs up?

WVZR-1

The self-test doesn't care if the car is going forward or reverse - if there's "no DIC indicators" and the car drives and functions normally after moving to the street I'd think it's very likely normal. I'd think the fact that he's resting a foot on the brake pedal it's felt.

Who is telling the "friend" he's got an issue?

I'm with SJW - I doubt an issue.

Your "friend" needs to be sure HE/SHE understands the self-test and also how it actually does function. The "self-test" is done every ignition cycle.

Does your "friend" have the FSM? I don't know how thoroughly the Owners Manual describes functions of "self-test" or ABS/ASR function but I'd suggest the "friend" does some reading OR talks to an owner that might help.

OVERULD

Thanks for all the input folks. The friend's name is Robert and he has owned this car as its second owner since about 1998, I think. He also has a 2013 Grand Sport. He does not daily drive the car but does start it and move it often between drives. I think the problem started earlier this year and the first thought was a booster, which was replaced, and the brakes bled. But the problem didn't go away, so I believe he then took it to the shop of a mutual acquaintance who formerly owned an auto service business. They re-bled the brakes and checked diagnostic codes, and I believe it was then that they decided it must be in the EBCM.

I've given him a link to this thread and I believe he is monitoring it. Hopefully he can chime in with some input which I will certainly post here.

Thanks,
BJ