'90 s2 abs?

rallyho · 08-01-2016, 12:53 PM

May sound like a silly question here...but I have a '90 S2 that has no ABS functioning. Fresh fluid, everything bled andhappy, no warning lights, etc...but have confirmed after a track day this weekend that if this thing actually has ABS, it isn't working.

So, looking to confirm that this car came with ABS, where the pump is if I have one and what I would do to fault-check?

thanks folks!

Mike

jhowell371 · jhowell371's Garage

On the track when braking really hard I thought my S2's rotors had warped until I realized it was the ABS kicking in. It doesn't feel like the ABS in my Chevy truck and my Ford Escape, much more subtle.

944 Ecology · 08-02-2016, 03:44 AM

Quote:

Originally Posted by rallyho

May sound like a silly question here...but I have a '90 S2 that has no ABS functioning. Fresh fluid, everything bled andhappy, no warning lights, etc...but have confirmed after a track day this weekend that if this thing actually has ABS, it isn't working.

So, looking to confirm that this car came with ABS, where the pump is if I have one and what I would do to fault-check?

thanks folks!

Mike

Your car was shipped with ABS.

The ABS pump is located in the right front fender well, behind the plastic fender liner. The ABS control unit is located under the dash near the A pillar on the passenger side. Each wheel has an ABS speed sensor.

The ABS warning light should light for several seconds when starting the car, then should go out if all is OK. IF there is no light, it may have been removed by a PO.

Common faults include bad wheel sensors, bad control unit, bad relays, bad fuses and bad ABS pump. The pump can be rebuilt. Other manufacturers use the same pump, but installed it in a location less likely to be hit by road salt and other debris.

rallyho · 08-03-2016, 08:39 AM

Thanks for the responses. I hadn't thought about the ABS light being out or unplugged. Caveat, I've never driven a 944 with ABS, so I wouldn't know...but the car stopped incredibly well without it. I will need to dig into this to see what's going on.

Curious, do folks find it intrusive in track driving and do you pull the fuse or otherwise disable it?

JeremyD · JeremyD's Garage

works fine on the track or the street

That said - if you have a bad sensor - then none of it works

There are trouble shooting procedures on line - I looked to see if there was any obvious damage - one of my rear sensors had a bunch of shavings - on it - I replaced it - disconnected the battery to reset the system - and pronto - started working again.

944 Ecology · 08-03-2016, 10:14 AM

ABS is good for the track... eliminates brake lockup and tire flatspotting, as long as it works...

Good in the rain, allows you to steer while braking at the limit of adhesion.

djantlive · 08-04-2016, 10:06 AM

When you first key the car to on position, does the abs light come on at all?

rallyho · 08-04-2016, 10:56 AM

Key at First half(?) position, nothing at all on, 2nd position, ABS, Brake, Airbag lights on, Car started the Airbag light and "!" stay lit for 3 seconds or so then go out.

924RACR · 08-06-2016, 03:45 AM

Fuses, relays, power and ground to the ECU are usually pretty easy to test (and cheap to fix), I'd start there.

Sounds from your last post that the ABS light does come on when you go to ignition on?

944 Ecology · 08-06-2016, 05:33 AM

Quote:

Originally Posted by rallyho

Key at First half(?) position, nothing at all on, 2nd position, ABS, Brake, Airbag lights on, Car started the Airbag light and "!" stay lit for 3 seconds or so then go out.

This is part of the startup test that the ABS control unit does every time.

Now that you know that the light works as it is supposed to, the ABS will light that bulb if you have an ABS problem. Since you stated that there was no other symptom than your perception that the ABS was not working, I conclude that the ABS is working as designed.

That said, keep in mind that the ABS of the late 80s was not nearly as sophisticated as the new ABS. I'm pretty sure that the ABS on a Honda Odyssey is much more sensitive than your Porsche.

For a real test, take your car out in a couple inches of untreated snow. I'm sure that you will be able to invoke it without too much trouble.

rallyho · 08-07-2016, 01:40 PM

Thanks all. This is good stuff. Correct, ABS light....lights. So no blown bulb. Never owned a Honda, so not sure how they keep minivans on the road, and certainly don't know what Porsche's ABS algorithm looks like, but pretty sure it doesn't allow full lockup of one or more tires. Confirmed full lock up with both street tires and gummy track meats. I'll start tracing grounds, relays and such.