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My "ABS Inop" light has been on for years. ...no biggie really, the front drivers side caliper will lock up under heavy braking, but the car is still compliant.

Today, *every* red light that I stopped at saw normal brake pressure from speed down to about 15/20mph, at that point the pedal drops about 1/2 inch, braking power is severely reduced, then around 5/7mph I get full braking power back and am thrown forward. Durning this time the "low-trac" light lignts up.

I have experienced this many times before, but, once every few months at most. Today, it was every time I stopped.

...also, the "ABS Inop" light is no longer on. I always suspected I had the light because my 3rd brake light is disconneted, I mean, when I swapped out rear hatches, the light appeared. In the past when experiencing the low-trac / loss of brake pressure, the ABS Inop light was still lit.

Wondering if a dirty wheel-speed sensor might be to blame, or, the ABS pump itself.

If it's the pump, can it be "bypassed" somehow? I don't really need ABS and given the systems current state of operation, I don't need to bump into the back of a Mercedes @ 10mph either.

If it's the speed sensors, where is a good source to get a replacement. ...or, is there a preferred method of cleaning them?

1993, LT1, 175,000mi, all OEM from booster to calipers. Calipers are new.

Ideas? Suggestions?

Thanks!
 

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1994 Firebird Formula 381ci LT1 / TH400+GV O/D
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I had a similar problem when the rear sensor on my Strange 12-bolt got out of adjustment (factory sensor not adjustable). This would suggest there is a possibility the rear sensor is covered with metal particles, or defective. The sensor can be removed from the top of the diff housing and cleaned or replaced.

The front sensors are embedded in the wheel bearing/spindle cartridge that mounts in the steering knuckle. The entire cartridge would have to be replaced. Some have suggested using compressed air to blow dust from around the sensor, but I have no idea if that works.

If you had a defective sensor there would be a code in the EBCM, and the "ABS INOP" light would be on. Sort of odd the light would go out and the ABS would work if you never reconnected the CHMSL. Not sure why you wouldn'tt fix it.
 

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Thanks Fred. I'll start by cleaning the fronts with compressed air (and get back to you on it). I have been driving down a lime-rock road daily as of late, maybe the fronts are "dusty", but, sounds like the best place to start. I'll scan the computer tomorrow, I never thought to do that since there is no check engine light.

I never reconnected the 3rd brake light because the hatch was from another year and the wiring is a different color. I was going to get around to looking up the colors and reconnecting it *after* paint, but it seems paint is never going to happen. I found it odd the ABS Inop light went out as well, I actually inspected the hatch wires at a stoplight just to make sure they weren't touching/grounding against anything and they weren't...

When I start the vehicle, The ABS Inop light is off (after key-on diagnostic checks), but as soon as I touch the brakes it illuminates and stays on at all times until I shutdown/restart, as I said, it's been like this a long time, probably 4 years. I always assumed it was the 3rd brake light, or, at least related to the mess I had with my tail lights/turn signals/brake lights because every connector but the corners was corroded and rusted very badly. I had to cut back quite a bit to get to fresh copper.

...again, thanks. You've given me a place to start, I'll let you know what happens.

Happy New Year.

...wow, on FBN for New Years. I think last time that happened was around 04/05 or 05/06. I remember someone had a radio station going. My profile says "Member Since 28 Apr 2006", but, that doesn't seem right. Maybe that's when the website migration happened?
 

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1994 Firebird Formula 381ci LT1 / TH400+GV O/D
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Do you have access to a scanner for the EBCM.

ABS problems do not turn on the SES light.
 

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Discussion Starter · #5 ·
I have Scan9495.
 
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