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jfoxny

PSM Failure, Spoiler Failure, Check Engine Light

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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 - btw, I had them try to reprogram the control units and that did not fix it). However, that to me doesn't seem to explain all of these issues. I found someone on another forum 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

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Just wanted to clarify that I drive the car year round in the Northeast and the problem went away during the winter but now that the temps are rising again it's back. I'm guessing that's a clue. Also, the battery was replaced right before these problems started (around this time last year). I had the techs check the connection and they assured me that it was sound.

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I will let others chime in but to start here's a little information.

First, the "limp mode" you describe is normal when the computer detects a "serious" problem. Specifically this is to keep the engine and other components from being damaged as you drive it in to service.

Second, while not completely the same, I can't help but to notice some very similar symptoms to when my previous car (a Carrera 4S) had a bad alternator and/or wiring harness. For one, you say this seems to happen the most when the weather is hot. Specifically with respect to that wiring harness, resistance builds as heat increases....and this problem also occurred in my situation on one of the hottest days of the year. That's no coincidence. The wiring harness is a known culprit in these vehicles (been revised at least a couple times and I think there's even a TSB on it) and if you do a search on this you will find tons of info and posts. A failing alternator or bad wiring harness, like many electrical issues, can manifest itself in a number of odd kind of ways. With mine I got the " ABS/ PSM" errors you are describing as well as some other weird gremlins like that. These components can throw errors when they aren't getting enough juice.

See what others have to say but this would be the first thing I would check. JFP and Ahsai recently just posted some really good/simple information on how to test this that I think you would find really helpful:

http://www.renntech.org/forums/topic/44471-voltage-regulator-affected-by-heat-hence-low-voltage/

Edited by Silver_TT

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Second, while not completely the same, I can't help but to notice some very similar symptoms to when my previous car (a Carrera 4S) had a bad alternator and/or wiring harness. For one, you say this seems to happen the most when the weather is hot. Specifically with respect to that wiring harness, resistance builds as heat increases....and this problem also occurred in my situation on one of the hottest days of the year. That's no coincidence. The wiring harness is a known culprit in these vehicles (been revised at least a couple times and I think there's even a TSB on it) and if you do a search on this you will find tons of info and posts. A failing alternator or bad wiring harness, like many electrical issues, can manifest itself in a number of odd kind of ways. With mine I got the " ABS/ PSM" errors you are describing as well as some other weird

Thanks for the reply and pointing me in that direction; I will check it out when I get home. To clarify, in your case, they replaced the wiring harness or the alternator or both?

I have heard of the wiring harness issues, specifically with the cars not wanting to re-start after getting hot. I personally have noticed slow cranking on a hot day or after driving for a long time, but, it's never refuses to start. Perhaps, it is the same issue though. I am taking the car in tomorrow and will mention this.

Thanks again,

Jason

Edited by jfoxny

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In my case it was definitely the wiring harness.... and the alternator was working well except for at certain RPM ranges (which made it a little difficult to troubleshoot). The alternator had 85K miles on it anyway, is only about $350 for the Bosch replacement reman, and needs to come out when you do the wiring harness I'm referring to (#21 if you read Ahsai's post in the link I shared with you above) anyway. In your case and the case of many others, it could definitely be just the alternator alone or just the wiring alone.

p.s. The test, as Ahsai described in that post, is very simple and should not take long. They can also psedo loadtest the alternator with it in the car and this takes just 5 mins.

Edited by Silver_TT

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As others already reporting electrical problems can cause strange problems, anyway it looks like that the reported problems are all speed signal related. In this context a problem with the ABS system is not too far away since the unit is responsible for the further distribution, to other control boxes, of the speed signal. It is perfectly possible, with a PIWIS, to determine whether the signal arrives in to the unit or not, and whether it is further distributed. A weak signal can be caused by a too high resistance in the wiring/connectors, etc. due to corrosion and can be temperature related.

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Best to get the fault codes - but many strange electrical things happen with a bad battery or charging problem.

Here are the fault codes from last year when I brought the car to the dealer while the fault was up. Only the PSM Failure was active this time (not the Spoiler Failure or Check Engine). However, I want to stress that the problem stopped happening during the cold months (I drive it every day here in Upstate New York) and then started happening again now that it's hot and wet (we've been getting a ton of rain here).

Control Unit, Priority, Fault memo, Status, DescriptionPSM, 1, C101, ACTIVE, Control unit faulty (No fault symptom available)PSM, 1, C150, ACTIVE, Communication DME control unit (drive) (No fault symptom available)PSM, 1, C153, ACTIVE, Communication steering wheel electronics unit (drive) (No fault symptom available)SEAT MEMORY, 1, C152, ACTIVE, Communication PSM control unit (drive)DRIVER'S DOOR, 1, C174, PASSIVE, Fault, convertible top control unit (comfort) (Signal implausible)PASSENGER'S DOOR, 5, C174, PASSIVE, Fault, convertible top control unit (comfort) (Signal implausible)

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Best to get the fault codes - but many strange electrical things happen with a bad battery or charging problem.

Here are the fault codes from last year when I brought the car to the dealer while the fault was up. Only the PSM Failure was active this time (not the Spoiler Failure or Check Engine). However, I want to stress that the problem stopped happening during the cold months (I drive it every day here in Upstate New York) and then started happening again now that it's hot and wet (we've been getting a ton of rain here).

Control Unit, Priority, Fault memo, Status, DescriptionPSM, 1, C101, ACTIVE, Control unit faulty (No fault symptom available)PSM, 1, C150, ACTIVE, Communication DME control unit (drive) (No fault symptom available)PSM, 1, C153, ACTIVE, Communication steering wheel electronics unit (drive) (No fault symptom available)SEAT MEMORY, 1, C152, ACTIVE, Communication PSM control unit (drive)DRIVER'S DOOR, 1, C174, PASSIVE, Fault, convertible top control unit (comfort) (Signal implausible)PASSENGER'S DOOR, 5, C174, PASSIVE, Fault, convertible top control unit (comfort) (Signal implausible)

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Yep, it sounds like you have an electrical issue related to what was described above. I'm guessing it's not the battery since you said above that you just had it replaced, but this wouldn't be the first time a battery had a shorter than expected life and it never hurts to test it since it's so easy and fast to do. As Loren stated, strange things happen when you have a battery that's not 100%.... and similarly when you have a faulty wire/connector all the way down to each respective component.

Again, regarding it only happening when it's hot -- that's not a surprise at all for reasons stated above.

If it's not at the front-end of the downstream electrical flow, as I alluded to, I think RFM brings up some good points in his post #7 above. It definitely feels like you have resistance in one of the wires leading downstream to these components throwing errors. To troubleshoot you are going to have to check each segment in the electrical flow leading downstream, starting at the battery, to narrow down and isolate where the issue is.

Edited by Silver_TT

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I read the post you directed me to last night but I didn't have the tools to do the diagnosis. I am at the dealer now and am pushing them to try to look for a voltage drop. They claim that they would see a "low voltage fault" if there was a voltage issue in the system, which they are not seeing. They did notie that it is cranking slowly and said they would try to figure out why that is happening which might lead to something. However, the tech said he feels that they are separate issues. :-

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They said 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 (?). They also said the slow crank is 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?

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Nothing like German engineering. All these systems are so interconnected you get the domino effect. In my car a faulty PCM made it look as if the PASM, TPMS, Gateway module and the instrument cluster were all faulty. Replaced the PCM and everything worked fine (with a little reprogramming) The dealer replaced the gateway module and the $4000 Yellow instrument cluster before the tech realized that it was the PCM all the time. He figured it out by simply unplugging the PCM. No PIWIS required.

I am certainly no expert but If the starter motor is drawing to much then it has a shorted armature or perhaps a bad relay. The starter motor circuit is most definately connected to everything else. For instance if your steering wheel is locked the car will not engage the starter.

I would fix the starter motor and see if everything else goes away before you get all wound up with the PSM. Good luck and please let us know what happens.

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The starter is drawing 340 amps which is apparently really high. I might start there are you suggested if I cannot get the warranty company to cover the big ticket item. Speaking of the warranty company, does anyone know if fault codes remain when the car is shut off (and if so for how long)?

The warranty company wants to see an active fault. They suggested waiting until it happens, driving the car to the dealer, then leaving it off until the inspector can get there. Will the fault code still be there until the car is started or do they clear when the car is shut off?

Jason

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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.
Edited by jfoxny

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The starter is drawing 340 amps which is apparently really high. I might start there are you suggested if I cannot get the warranty company to cover the big ticket item. Speaking of the warranty company, does anyone know if fault codes remain when the car is shut off (and if so for how long)?

The warranty company wants to see an active fault. They suggested waiting until it happens, driving the car to the dealer, then leaving it off until the inspector can get there. Will the fault code still be there until the car is started or do they clear when the car is shut off?

Jason

Fault codes are stored until either cleared by a tech or until the DME feels that the problem has been solved or repaired, which is often quite a bit of driving (several start, warm up, run at highway speed, shut off, and cool down cycles at a minimum).

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Fault codes are stored until either cleared by a tech or until the DME feels that the problem has been solved or repaired, which is often quite a bit of driving (several start, warm up, run at highway speed, shut off, and cool down cycles at a minimum).

Thanks for the reply. That's great news. Then perhaps their suggestion will work. The warranty company also wanted verification that the dealer contacted "Porsche Technical Support" to consult them / open a case regarding this issue. Is that a normal thing for the techs to do? I'm going to call the dealer tomorrow and see if I can find out what the warranty company is talking about.

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I have been through low voltage symptoms like windows not closing fully when the door is closed, slow cranking

I am sure you have done that already, but what about charging the battery for one night, if you notice a difference you know that you either have an alternator or a cable to change

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Fault codes are stored until either cleared by a tech or until the DME feels that the problem has been solved or repaired, which is often quite a bit of driving (several start, warm up, run at highway speed, shut off, and cool down cycles at a minimum).

Thanks for the reply. That's great news. Then perhaps their suggestion will work. The warranty company also wanted verification that the dealer contacted "Porsche Technical Support" to consult them / open a case regarding this issue. Is that a normal thing for the techs to do? I'm going to call the dealer tomorrow and see if I can find out what the warranty company is talking about.

Aftermarket warranty companies thow all sorts of road blocks into the process, which is why a lot of shops do not like them.

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Jfoxny, 340 amps??? That would melt the car. Maybe you meant 34.0 amps? Remember your average household circuit is 15 amps. My self cleaning electric oven is on a 40 amp circuit. Fix the starter. If the PCM module has an issue it will at some point become obvious and you can shove it down the insurance company's throat. I will gladly help. Please let us know what happens. Experience is the best of all teachers and here we get to share each others experience!

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340 amps is possible but very high. The clue is your battery. They quote for example 80Ah 360 CCA this means it will supply 80 amps for one hour and can produce up to 360 amps peak current under cold cranking conditions. This is why your earth lead and the supply lead to the starter are so huge! In domestic systems 110/115 volts US 220/240 volts UK they are roughly 10 and 20 times the voltage (ignoring the DC versus AC as it gets too complicated!) hence 10 to 20 times less amperage for the same job. Example 60 Watt bulb in US will draw about 0.5 amps, in UK about 0.25 amps but in a car 5 amps, hence the larger cross sectional wiring to cope with the higher current (amps) Volts x Amps = Watts HTH?

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Jfoxny, 340 amps??? That would melt the car. Maybe you meant 34.0 amps? Remember your average household circuit is 15 amps. My self cleaning electric oven is on a 40 amp circuit. Fix the starter. If the PCM module has an issue it will at some point become obvious and you can shove it down the insurance company's throat. I will gladly help. Please let us know what happens. Experience is the best of all teachers and here we get to share each others experience!

No, it says 340 amps on the work order and he also told me that verbally. The problem continues to happen sporadically, however, I need to have it happen at a time when I can get the car to the dealer. The warranty company asked that it be brought there and left un-started until the adjustor can get there. I'll post when I am able to do that. Fingers crossed!

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jl-c is right. Senile old me forgetting Ohm's law and it's derivatives. But, your starter is still bad an needs to be fixed. So, I would still treat this as two separate issues. Your warranty company can not argue the starter. Fix it first before you torch your battery which probably is not covered under warranty. Then watch the PSM problem. When it faults have your tech take a picture of the computer screen showing the code.

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This problem is still happening on occasion. When I turn the key to the accessory position it almost always throws a PSM Failure / System Failure fault. Recently got myself a Durametric tool and scanned the car after one of these faults appeared. Here's the set of fault codes (similar to the previous set from the first page):

U0129 - Unkown fault code
P0564 - Cruise control operating lever
P0503 - Vehicle speed signal
C152 - Communication PSM control unit (drive)
C202 - Fault PSM control unit (display)
Not sure if this provides anymore clues as it seems pretty similar to the original set. But, I figured I'd follow-up now that I have the Durametric. Maybe there's further diagnosis that I can do with the tool? I'm new to this tool.
Thanks,
Jason

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C202 Diagnosis information CAN - Fault entry in specified control module
Possible fault causes
- Control module is incorrectly coded
- Periphery connected to specified control module is incorrect
- Control module faulty (in most cases the cause is not the control module but incorrect coding!)

C152 Diagnosis information CAN - PSM control module, communication

Possible fault causes
- No power supply for PSM control module
- PSM control module incorrectly coded
- Short circuit or open circuit in the CAN drive
- PSM control module faulty (in most cases the cause is not the PSM control module but incorrect coding!)
You have checked the grounds on the car?
I would try re-programming the PSM module - clear the codes - then see what comes back.

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