wf758

Lynn,

Do a search, there are several posts on how to do it.

As for shops, try sending a PM to Steve (deep_uv). He is a nice guy in Austin and can probably make a recommendation.

Will

frankvan

Well I've done some further investigating on my ABS/PDAS problem.
Voltmeter shows 12.8 with engine off, 13.7 to 13.8 at idle.
Cleaned contacts on all four relays (two in the fuse block and two on the ABS pump),
re-cleaned the contacts on the big connector to the control unit and the four pin connector on the smaller unit just aft of it in the front boot.
tried different fuses in positions 15 and 16 in case bad contact point there.
Hooked up Scantool and got the following:
15 - Control Unit Defective
34 - Valve Relay (which one is the valve relay???)
7 - Unknown Trouble Code.

That last one - unkown trouble - concerns me!

When I get the chance I'm going to pull the wheels and clean the speed sensors and check their connections and grounds.

frankvan

Pulled two of the speed sensors and they seemed fairly clean. Cleaned those two anyways and stil get the ABS error.
I've noticed that just before it lights up I occassionally get a flicker of a XMas tree effect (all the lights on the oil gauge flicker but the ABS/PDAS lights stay on).
Could this possibly be leaky coils, dist caps or ignition wires? (I've replaced the main ignition leads and the 6 wires on the drivers side already, but the passenger side requires a bit of time that I just don't have right now...)
The only things I've done to the car since this problem has gotten bad is a valve adjust and replaced the autothority chip with a stock unit.

frankvan

Just to update this thread, I replaced the coils about a month ago and haven't had any PDAS lights since. So, even though the car ran fine on either coil it would seem that one of them was bad enough to cause electrical noise that would confuse the PDAS/ABS system. talk about a sensitive system (it's brains are even located at the opposite end of the car from the coils!)

amr89c4

Hey Frank, thats great news. Glad you got the gremlin out. I agree with you on the sensitivity to rfi. I'm in the marine propulsion business and we see some pretty weird things happening to gps units, radios, radar and engine alarm systems, so nothing surprises me anymore. Glad the coils got you going!

altarchsa

I have had similar frustration with the PDAS / ABS warning combination. I'm just as frustrated as you sound. I am also slowly moving through the checklists. Have two more speed sensors to do then will try cleaning the accellerometers.

I couldn't believe a recent post that said new coils had fixed his problem. I bought coils even though the car seemed to run on each coil independently. For two days the incidence of warning lights is greatly reduced but not completely gone. The car has SO MUCH MORE POWER now, I'm glad I replaced the coils. Have a set of wires on the way which can't hurt. I know the #3 connector is split at the top.

Weirdest thing I have found, when I wash the engine compartment, PDAS /ABS lights go away until the car has had enough time to completely dry out, usually overnight. I thought it had to be a bad ground at the rear wheels and the water was completing the contact, so those were the two sensors I cleaned. Also removed, cleaned and refit the ground wires, but still not completely solved. I appreciate everyone's advice on these forums. It's really helping me narrow it down. I'll get it someday, but it's terribly frustrating.

Cody D

Where did you buy the Coils from? I just paid $340.00 for a wheel speed sensor that didn't fix anything.

amr89c4

Cody D and altarchsa, see my post on 11-4-07 and you can see what all I checked before I got to the accelerometers. I'd link it to here but I am computer challenged. Like you, I had a lot of hours in the project. Don't give up. Its just a car. Well, it is a Porsche 964, so its not "just a car". In fact, they are our Porsches. Man that feels good.

frankvan

http://www.autopartsway.ca/AutoParts...~Ignition+Coil

or

http://parts.autopartsonlinecanada.c...=Ignition+Coil

(no affiliation, etc...)

If you're in the US of A (or the Republic of Texas) Pelican or another supplier like Vertex or Sunset might be better than a Canadian supplier (except for ignition wires which seem to be 1/5 the price in Canada! ) If you go to Pelican Parts they have them at a reasonable price (around $55 as well i believe). (again no affiliation, YMMV, etc...)

BTW, I have to give credit to DFinegan for the solution to my particular problem! (thanks Dave!)

Cody D

Thanks Frankvan, I just ordered two from one of those links.

dfinnegan

Frank, you are more than welcome, though, to be sure, I don't deserve credit for the fix. I may have suggested the coils, but only after you had received a lot of good advice here already.

I figured that I'd seen a number of bad coils here lately and had read a comment by one of the true experts that our coils are getting a bit long in the tooth and at $50 each it's not a bad investment at any rate.

Just glad you found your solution.

In truth, I still fee that I owe you for your assistance in other matters! :-)

Cheers,
Dave

altarchsa

I shopped coils at Pelican, but found another supplier Autohausaz.com that has better prices. I've had good luck with them on several orders. Coils were mid-$40's as I recall.

Wound up buying them from a small foreign parts house here in S.A., former Peugeot dealer of all things. But I've been buying parts from them for 20 years and they have great relationship with Bosch. Paid about $10 ea more than web + 5 day shipping, but got them next day.

kalujo

Sounds like this is a common problem,I'm having very similar symptoms to you,and have also tried all the sugestons you have done,like you I am still getting the ABS light,buzzer etc.I think I've narrowed it down to either one or more of the speed sensors,or the ABS control unit .Next thing for me is to discount one or the other.
I'll keep you posted how I get on.
Keep smilling,these are all part of 964 ownership.(I'm told)

frankvan

kalujo,
do you have access to a Bosch Hammer or the Scantool software? They might help with narrowing the problem.

kalujo

Frank;
No I don't have access to a Bosch Hammer ar Scantool software.
Next step is an apointment at the main dealers(250Kms away)so it will be a few days before it can be organised.There are no Porsche specialists in my area (S.W.France),lots of tractors!!I'll post as soon as I get some results.