'94. Quick one today - hopefully someone with ABS experience can clue me in on some exact programming or known causes...

Just had a brake service done - all four corners of pads plus new fluid and a bleed. The brake pedal has always had a whoosh sound at the far end so I know the booster is probably on the way out, but the car stops fine if a bit squishy to the foot.

I did a few brake checks earlier at around 25-30mph. Foot right off gas and all the way to the floor on the brake. No squealing tires (it's down on pressure from the booster, I'm sure), no lockup, but very worryingly was the lack of the ABS activating. No codes are set and the startup lights & 4mph pump groan check all work like normal.

Really I'm just curious to know if our cars have anything very known in the ABS system to wear out (like the opti for ignition problems!) that I can check first. Otherwise I'll load up the parts canon and start firing bearings and speed sensors. And a new booster / master cylinder.

TLDR; ABS doesn't function and has no codes about it.

Thanks as always!

 

Upon acquisition, I had to work on/with the ABS in my 1992. One valve/solenoid was not functioning, and that wheel (RF) would lock during a hard stop with no running of the module. Using my Tech-1 with a BRAKE cartridge, I was able to free up that solenoid and proof the system that the ASR and other components, etc were functional. Afterwards, from time to time I purposely engaged the ABS to ascertain that it was still functioning, and to "exercise it".

About a year ago the plastic booster failed and I had to replace it with the metal one as that is all that is available now. The brakes have never felt as good or strong as they were with the OEM booster. I don't recall that I have ever been successful initiating an antilock stop since the booster change. With the anemic boost of the replacement booster, I'm not strong enough to push on the pedal hard enough to lock the wheels, and being a 6-speed the brake pedal isn't big enough to use both feet. So I haven't exercised the ABS in the 92 for over a year now.

What I may try, and I suggest that you try as well to ascertain that the ABS is or is not functioning: Overinflated tires provide less traction and should lock-up easier so air up the tires to about 45psi. Then try an ABS stop. A rainy day might also provide an opportunity for testing, but only in conditions where there is absolutely nothing to hit. If the rears lock, you can loose control quicker than you can react to it. (Been there done that.) Keep in mind that the wheel lock must occur prior to the speed decreasing to 15MPH. I generally initiate my tests at 40-45 MPH. I push harder and harder with the ABS engaging at about 30-25MPH. I don't just mash the pedal. If a wheel locks and stays locked there is probably a stuck solenoid. The motor may or may not run (mine didn't.) There probably won't be any codes, especially if there is no SVC ASR or SVC ABS light. Mine didn't have codes.

I presume that you know that you can query the ABS/ASR codes with the onboard diagnostics. #5 & #12, Module 9.

TL;DR: Air the tires up to 45 psi and initiate your 'harder and harder pedal pressure' stop at 40-45 MPH.

 

I will try that with the tire pressures - I also didn't know about the 15mph threshold, so I'll certainly try it from a higher speed. Also duly noted about the brake booster. The one that came on the car really doesn't look all that old next to the rest of the engine bay so it's possible that it's already one of those less-great replacements. Will look into the solenoids, too. Will update as I have a chance to test things

Thanks!