jfoxny

I have been having a periodic problem with my 06 997 cabriolet (manual, non-PASM, sport exhaust) which seems to return when the weather is hot and I'm hoping someone out there can help.

Sometimes when I start the car (apparently when it's hot out), I get a "PSM Failure" message. This message is sometimes accompanied by a "Spoiler Failure", other times accompanied by a "Check Engine Light," and yet other times will appear by itself. I've also had a "Spoiler Failure"/"PSM Failure" message appear when I hit speeds that the spoiler should deploy at. The error(s) usually clears after driving for a while then restarting. Though, the check engine light sometimes stays on for days before clearing itself.

Possibly another clue, I have also noticed that when the error messages are active, the throttle responds in a strange way; if you left off the throttle it drops revs hard with a "thud." Sometimes it refuses to rev over 3k; like it's in some sort of "limp home mode" and sometimes the sport exhaust will not engage.

I've had the dealer scan the car when the "PSM Failure" was up, but, the result they came back with was a faulty ABS Pump (about a $5k repair). However, that to me doesn't seem to explain all of these issues. I found someone on another thread with similar issues and they had a faulty relay in the passenger side door (I am going to take the car in again tomorrow and mention that one).

Anyways, I'm hoping someone out there has either experienced this before or can help diagnose.

Thanks in advance,
Jason

IslandS52

I did not have you other symptoms, but I struggled for a few weeks diagnosing the following on my own car...
Possibly another clue, I have also noticed that when the error messages are active, the throttle responds in a strange way; if you left off the throttle it drops revs hard with a "thud." Sometimes it refuses to rev over 3k; like it's in some sort of "limp home mode" and sometimes the sport exhaust will not engage.

It turned out to be a failing electronic throttle body. I repaired it for about $275 for the part and did the installation on my own. The car would also give me the message "sport mode failure".

997_rich

With such a disparate range of electrical failures I'd make sure you're cool on power. I think I'd doublecheck that battery and proactively replace it if it's over 2 years old. The next thing to double check are the battery cables that run the length of the car. Sometimes they oxidize and the voltage drops causing odd failures. There's a TSB on this.. you can find more if you do a search on cables.

If all that is checking out.. I think I'd look at the wiring diagram to see if they're all on the same wiring harness (a few of them are but I think the ABS is at the front of the car).

Another possibility is just a bad computer, usually they don't fail this way.

jfoxny

The battery was actually replaced right before these problems started (last year around this time). I had the techs double check that the battery connection was sound and they assured me that it was.

What I find suspicious is that all winter (I drive the car year round in the Northeast) it was fine, however, now that the temps are soaring, the problem has returned. Is that a clue?

BTW - here is the output from the PSM Failure scan from last year which the dealer said indicated a ABS Pump failure (specifically part #997-355-955-06)...

jfoxny

Interesting. I don't have the Sport Chrono Package, so, I don't have "Sport Mode." However, I believe the throttle is still electronic. I will mention this to the techs tomorrow too. My guess is, however, that the failure of the stability management might limit throttle response - though - that is a total guess on my part.

997_rich

This is a big clue to me. If the techs were monkeying around with the battery and trouble showed up shortly after I'd be looking really closely at whatever they did. Maybe you got a bad battery, maybe they just didn't tighten the electrical connection well, you hit a bump the voltage drops and then you get an error. Maybe the heat causes something to expand and then disconnect etc. Maybe the battery connectors are broken right where the wire goes in but the terminal clamps are tight etc.

jfoxny

Yeah, this is the first place I started. I'll have to lean on them to double check this again. Initially they said the fault would clear after driving, which I've read is true, and did indeed happen. But, then the fault reappeared under various conditions and they could never get a scan on it because it would clear every time I restarted the car. So finally one day I drove it there with the fault up and they got the scan that I posted above. After that it was a closed case to them.

I tried to get the warranty company to cover the issue but they would not cover it unless THEY could reproduce it. Since it was a sporadic electrical issue I was SOL. The problem went away during the winter, and I just crossed my fingers that it sorted itself out but, now it's back in full force. :\

I will push them to check the battery and associated items tomorrow for sure. Thanks for your replies.

Jason

jfoxny

I'm at the dealer now. I had them check the battery connections as well as check for voltage loss between the battery and alternator based on the advise over at Renntech. The techs said the battery connections are sound and that they tested the voltage from front to back and throughout the entire system it only lost 3/10ths which is within spec. They said their conclusion is that it's still the PSM control unit which I guess is part and parcel with the ABS Pump (?). I also had them check into a slow crank and they said that is being caused by the starter; it's drawing too many amps.

My problem now is that the warranty company (Fidelity Platinum Warranty - $4k) won't cover the PSM control unit unless their adjustor can physically see the PSM Failure error up on the Dashboard.

First, does the diagnosis seem sound? And second, anyone have any ideas how to get the failure to occur on-demand?

997_rich

The starters do crank quite slow on these cars(high compression, small starter gear) s o unless it's getting slower over time that sounds normal.

If the ABS is truly throwing faults in connection with the PSM control, I guess i'd start by driving 25mph and slamming on the brakes. You should get the ABS to kick in.

jfoxny

According to the dealer the starter is drawing 340 amps which is way over spec. If I can't get the fault to show up, I may try to replace the starter and see if that changes anything. Speaking of which, does anyone know if faults remain after the car is shut off?

The warranty company wants to see the active fault. They suggested that the next time it happen I drive the car to the dealer, shut it off, and leave it that way until the inspector can come. Will the fault codes still be there ore are they cleared when the car is shut off?

jfoxny

Here is the full report from the tech:

SCANNED SYSTEM FOR FAULT CODES. FOUND MANY CONTROL UNITS HAVE FAULTS FOR NO COMMUNICATION WITH PSM CONTROL UNIT. PSM CU HAS A NOT PRESENT CODE FOR "CONTROL UNIT FAULTY". DME ALSO MISSING SPEED SIGNAL AT TIMES WHICH COMES FROM PSM CU. RECOMMEND NEW PSM CONTROL UNIT. CHECKED STARTER CABLES DUE TO SLOW CRANK. FOUND VOLTAGE DROP OF .30 VOLTS BETWEEN BATTERY AND ALTERNATOR-OK. FOUND STARTER IS DRAWING 340 AMPS WHICH IS OVER SPEC-WILL NEED STARTER TO CORRECT. PART#996-604-103-X $304.02 PLUS LABOR TO INSTALL.