I have driven my 04 Jetta TDI about 3000 miles in the three weeks I have owned it, without problems. It now has 193,000 miles on it. The day after changing the timing belt, I popped the hood to double check my radiator fluid and apparently did not completely latch it all the way down. The next few drives that day I noticed the horn did not beep when remote locking the doors. The same day I went to a car wash and manaully spray washed my car and as I went to vacuum I noticed the unlatched hood. So this was the reason the horn did not honk, a nice feature I did not know about. Trouble came after this though as my CEL came on. Upon checking the code it indicated a MAF sensor problem and I looked under the hood and in that area and all looked well, not that that means much. The car ran normally so I reset the CEL to turn it off. Before and after the car wash I have not experienced any problems with the car. Having no other symptoms I feel somehow that the unlatched hood and the spray from the car wash sent a false reading to the computer, based on absolutely no experience with this stuff. It has been about 500 miles since then and there are no indications of any trouble. In total, the CEL came on after spraying the car with the hood not latched and other than the light being on there have been no problems. Just thought I would pass on this experience to the forum.