Long time lurker - first time poster...

So I bought a non-CPO 2011 CS a little over a month ago. In general I'm very happy with the vehicle but have an issue that I'm having little luck in resolving.

The Porsche dealership originally did a CPO inspection and found they'd need to replace the water pump (due to evidence of a leak some time in the past) and put new brakes all around for it to meet CPO standards. Since that would have raised the price of the vehicle outside what it should realistically sell for based on mileage they opted not to go down that road. I was OK with that as it's work I can do myself. Everything else on the car was marked as a "Pass" on the inspection report, of which I have a copy.

The ongoing problem part is that on the drive home I noticed that the PCM would not go into night mode or change brightness. The night mode problem seems to have been resolved by charging the battery. I also paid to have the PCM updated to the most recent version and it went from v2.40 to v2.47. However it still does not change brightness and seems stuck on +6 as the whites are very bright and it's way too bright at night.

The used car manager has just told me they will not fix it even though the paperwork says the PCM was working. He's saying this not because the car was sold as-is but because the salesman told me that the update may not take - go figure. I'm assuming at this point that since the PCM version shows as v2.47 that the update took just fine and that everything but the brightness setting seems to work. If I had known the PCM had an issue I would have either had it written into a "due bill" like I did with the PCM upgrade or would have passed on the vehicle since I know it may not be cheap to fix. To add to the problem the dealer is 2+ hours away.

I've left a message for the dealership GM saying I'd like to amicably resolve this but I'm willing to go to the BBB and/or Social Media - but I'd prefer not to go down that road.

Looking for other ideas/suggestions for a mutually agreeable solution other than I should have checked every aspect of the PCM before signing on the dotted line - since I already know that

 

Was the car sold with any kind of warranty? If so, check the exclusions. If not, that's the down side to a used car with no warranty. Assuming you have no warranty, it would be nice for the dealer to help you out some, but if he knows you are 2+ hours away he can safely assume that he probably won't see you for service appointments which reduces his incentive.

Have you tried replacing the battery altogether? You mentioned that it needed to be recharged, but these things have a habit of doing really strange stuff as the batteries age even if everything that normally indicates a battery/charging issue is fine.

I'm not clear on the upgrade you had them perform? Was it showing issues prior to purchase and you had them do the update to fix that? If so, why didn't you make it part of the deal? Generally Porsche only updates things if there is a Campaign (in which case you shouldn't have to pay for it) or if there is a specific complaint. As far as the upgrade "not taking" unless they were trying to do something outside of what PIWIS will allow (e.g. forcing an update from a different CDR system onto it) there should be no issue unless the unit itself is bad. So as long as that is a supported firmware version for your module, their "we told you it my not work" line is BS.

So if you have a warranty and the PCM isn't caught in one of the myriad of exclusions, then it should be covered. If there is no warranty or it is excluded, then you are on your own.

 

No warranty so I know I'm likely not going to win this one. The local dealer is willing to take a look at it so I'm going to stop by and he'll hook up the PIWIS as a courtesy to see if he can get things working or find an alternative solution like turning it down using the PIWIS.

I had the version upgraded from 2.40 to the latest it would take (2.47) in order to get the time on the PCM display as otherwise it's not visible to the passenger (wife). I negotiated that as part of the sale in advance and actually paid a reduced amount to get the work performed. Based on my daytime test drive and the CPO inspection I had no reason to feel there was a brightness issue with the PCM. I'm sure they're feeling like "Oh, crap" and thnk they'll need to caugh up for PCM unit which is why they're behaving the way they are.

When I took it in to get the update done and the leather work touch-up they promised (which I didn't expect but they offered) they did do a load test on the battery it passed. It's most likely the original since it's only 4 years old and the only other issue is the Auto Stop/Start drains down quickly when it stops so it restarts as soon as the battery gets to 12.0 volts. That's the only other weird electrical thing I've encountered so while the battery will probably need to be replaced next year if I didn't use the Stop/Start function I'd never be aware of it.

 

Yeap the battery will still pass the standard tests, but it will be just bad enough that weird stuff happens. If you search here and RennList you'll find some really bizarre things that cleared up with a fresh battery. If you expect it's the original, give that a try and see if it helps both the PCM and A/S issues.

 

I stopped by my local dealer on the way home and the Service Manager was kind enough to do some troubleshooting and hooked up the PIWIS. No ability to change the brightness so that was a bust. We also did a factory reset on it with similar results. Since I've got multiple keys he said I might try using one of the other keys to unlock the vehicle after locking it with mine to see if that had any effect since so many setting are store in the keys but no luck there either. I forgot to ask about the battery as a possible cause but will call them tomorrow.

I'll probably go the cheap route and find some tinted screen protector that doesn't interfere with the touchscreen if it's not the battery and I get no resolution from the selling dealer.

My guess at this point is that it's a bad cable or some such since everything else seems to work and it behaves the same even after the battery is fully charged.

 

I have just upgraded from PCM V2.41 to PCM V2.47. Picking the car up now I will let you know how I go

 

Maybe this is a US thing also. According to Porsche Canada and my local dealer a fix is now available. Apparently, the PCM software had a problem in that it recognised the daytime running lights as headlights and would not allow the switch-over. It would only allow the daytime mode if the PCM was set to daytime, thereby overriding the DRL. This has been corrected as of an August 2015 PCM update available at your Porsche dealer.Can the DRL be switched off on your Cayenne? If they can , try that.