2 warning tones were heart last evening on our way back from San Jose to Irvine, CA. The wanning tones were for 4 wheel drive failure then followed by PSM disabled. It happened about after a 290 miles drive. Because of the warnings, we decide to had a dinner in Los Angeles and see what would happen. After the dinner, I start the engine again. The warrings were gone, and PSM was also back to work. Anyone has this experience before, should I bring my car back to dealer for check up

 

That sounds like a variation on the gremlins which occur from time to time. I would report the incident but I would not give up my car for them to play with it.

 

The system faults, that caused the PSM and 4-wheel drive warnings, are now stored within the module's memories.

In theory, the presence of these faults should not cause additional failures. However, the dealership could connect to the external CAN bus connection, interrogate these modules, as well as the others, then clear all the stored faults.

It may be that there are negative aspects to having the dealer perform these steps, then report on the results, but I don't think so.

 

Thanks, I just called a dealership this afternoon. They said if the warning was gone, then I should be fine. Also, if one of the wheel was off raod, it may cause the warning. I may drive too fast on a not so smooth L.A. high way.

 

We also have had this failure warning, while we driving on a straight and level road? The dealer could not find the warning/failure in the system. so its buried somewhere in the system..

 

Every system failure is stored in the module along with a failure code. This information may be observed by the dealer. It may prove valuable, at a later time, to have obtained and recorded this information. It may be that a component is deteriorating, inducing this failure, or it may be that this was a random glitch that will not repeat.

In either case, obtaining and recording the fault information is a good first step in resolving this problem.

 

This problem, with the PSM reporting a transient failure, has been experienced by two different users on this forum. It is reasonable to conclude that other Cayenne owners have also encountered this problem.

As such, it is also reasonable to conclude that PCNA and Porsche AG have the failure codes, obtained from dealers, when customers report this problem. With that data, they are enabled to analyze the problem.

In my opinion, members of this forum should also have this failure data. We should be enabled to examine characteristic problems and arrive at our own conclusions.

My recommendation remains, if any members experience this failure, please require the dealer to provide the failure code, so that it may be posted here.

The failure codes will still exist MAV's and in bojali's Cayenne, unless the dealer cleared it, or unless the vehicle has had over 50 cold start ignition cycles, so that data may still be available.