VS

I am wondering if any of you have experienced this problem: at full boost the tires loose traction and subsequently the "PSM/ABS failure" light appears. At this point the ABS shuts down completely. Bye-bye ABS.

One might think that swithching PSM off to start with would help. It doesn't. The same thing happens with or without PSM being deactivated.

Happened to me this Friday at Watkins Glen. As a result I locked up the brakes and flat spotted/corded the front tires. A perfect track weekend has been ruined

This should especially concern the owners of (Uni)chipped high HP cars ...

What is your experience?

VS

CJV,

This is very interesting and makes a lot of sense to me. I guess your point is that the problem has nothing to do with the traction/PSM but rather with the vacuum line being sensitive to acceleration? That would expain why this problem occures even with PSM turned off.

Did you have if fixed at The Racers Group shop?
I suspect details may be quite important in pinpointing the culprit.

Thank you very much for sharing your experience

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skaria

You just might have solved a problem which has been bugging me since I installed the UNICHIP last week. On full throttle, the PSM/ABS Failure comes on. In addition, I also turned off PSM to see if that would cause the problem to go away... just like yours, it still came on. I had thought that I screwed up something in the install (I believe the set of wires for the PSM is right next to the batch that you tap into for the UNICHIP, so I double and triple checked and everything was according to spec. I am going home now to figure this out... Thanks!

btw, does your failure lights reset also when you turn the car off?

skaria

Thank you CJV. I think sharing your knowledge and experience saved me $$$ at the dealer... if you ever come to Philly or NYC, give me a holler. I'll buy you a beer!

skaria@deshaw.com

VS

Skaria,

The light goes away after a power cycle. Wondering if you hear the tires break loose right before the failure occurs?

BTW, who programmed your Unichip if that's OK to ask?

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skaria

No, I do not hear the tires break loose before the failure. It usually happens in 4th or 5th gear when I am chugging along and got to full throttle suddenly. I do not get it when I accelerate from a stop, redline in 1st, 2nd, 3rd, etc. Also, like you, turning off PSM does not help.

My UNICHIP has the base program for the 996 Turbo w/o exhaust from The Racers Group. They are the sole distributor for it and they send the base program to dealers who do not have a dyno. I picked it up from a fellow Porsche owner and the install was a piece of cake. I am just trying to iron out the kinks right now. ;-)

cobra06

This has been an off and on problem of my car. They replaced the MAF twice because that's what the computer said the problem was. I mentioned cjv's brake pedal switch, and they quickly discounted it. Happen to be going to a different dealership for a tech inspection and brake fluid change and it happened to me on the way there under hard acceleration. ( hard to get it to repeat). Mentioned the brake pedal thing and he said , yes there is a service bulletin out on it but it throws a PSM code, which my computer is not showing. Told him about the MAF and he just laughed (I thought it was a stretch myself). He thinks its a vacuum line leak. Going back when he has a day to diagnose. Moral: there are good and bad technicians, some use the computer for a complete diagnosis, others use it as a clue and use their brain and experience to find the answer.

cobra06

cjv
Turning my car off then on resets the light as well. It did show a MAF failure on the computer.
I think I'll try to get my technician to call your guy, if the Ego thing doesn't get in the way.

cobra06

Chris G, left that dealership for parts unknown (they did say he was a very gifted mechanic)

VS

This afternoon I took the car the dealer to sort out the "Check engine" light problem. On my way there, I was at full boost and then let the throttle up abruptly. Boom! There was a loud popping sound. Aftern that, no boost whatsoever. Plus the dreaded "ABS/PSM failure" light came up again.

Right now the car sits at the dealership. I guess they will have to sort out all problems at once.

I was pleasantly surprised to see they had been aware of the "vacuum line theory" ... from reading this thread on the Rennlist!

Hoping for the best...

Oak

VS, sounds as one or both of the turbo hoses may have popped off, minor hose clamp tightening. If this is the problem you can upgrade the clamps, have you seen the type that Porsche uses for the turbos? Pretty wimpy. Good luck, keep us posted.

skaria

I took my car to the dealer (Brandywine Porsche in PA) today for an inspection and told them about the "PSM/ABS Failure" light issue. They checked the faults and there was none, so they said that they could not do anything about it. They did say that several other customers complained of the same problem and that they are waiting on a technical service bulletin from Porsche before they do anything. I told them about the "vacuum" theory, but they dismissed that... I am going to take the car now to my dealer in New York (Manhattan Motor Cars) and see what they say. They told me over the phone that there just got an update of the PSM software, but I do not think that PSM is the culprit here... seems brake related.

Garey Cooper

To add to this thread; very early on in my ownership of my car there were two vacuum lines replaced; 2 ea. #996-110-649-71. These are I understand not an uncommon failure source for 996TT's. During the time these were bad my car would show ABS/PSM failure light, this usually came on under acceleration. It was just a failure light, I do not think the ABS/PSM actually failed.

Also done at this time was;
1. Measure rod length on turbo waste gate
2. remove and install aircleaner element
3. check for leaks at intake distributor
4. R & R intake manifold and flush oil out
5. clean intake

Item 3 I believe refers to the stock Bosch diverter valves, these I replaced later in fact.

I asked to look at the vacuum lines as I was interested in the failure mode. However these were not shown to me as "all warranty parts are returned to Porsche for analysis" was given for not having them around. I do believe this and I think it speaks well for Porsche.

Note that when the original failure occured it was under hard acceleration and the car gave a POP and exhausted what I'd describe humorously as "fur ball"; actually a cloud of smoke.

Later my diverter valves failed and honked, unfortunately they sounded like French Horns out of tune. They were replaced with stock Bosch and after this I (as mentioned above) changed them out for Forge units.

I hope this helps! Hold out for the right fix, there are service bulletins out on all of this I think.

A last note; the dealer was very responsive once I got to talk to the mechanic directly.

VS

An update on my car.

Just as Oak suggested, the hose connecting one of the intercoolers to the intake snapped off. Apparently it was not attached properly at the factory. Over time, it was getting looser and looser. There were some early sympthoms but I tended to attribute those to the failed DV's.

A few days ago it got bad enough to cause the "Check engine" light to appear. Finally the hose snapped off completely: No wonder, it happened on an abrupt throttle lift under full boost. That's some "blow off valve" for ya!

The offending hose has been fixed and reattached. When the replacement (new) hose comes (they are on backorder now) they will install it. An overkill probably but it will make everybody happy so why not?

What about "ABS/PSM failure"? The current theory is that the loose hose was messing up the vacuum thus causing the problem. This would be consistent with all I've seen in my car so far. Now that the hose is fixed the "PSM/ABS" problem should be cured as well ... I hope.

To make sure we would have to make a few high acceleration runs. But it rains cats and dogs today! I tried but it is hard to hook her up
As soon as it dries up I will do the tests and post the result.

Thank you all for the support. Special thanks to CJV and Garey Cooper for the first-hand information on the vacuum line link.

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