I flew back from Zürich to Toronto this morning, and Alex came by my house this afternoon with his Phaeton, and the two of us got to work.
First thing we did was to run a diagnostic scan on the vehicle. There were no faults present in the Central Comfort Controller (controller 46), which is the 'master' controller that the power trunk lid controller is slaved to.
Next thing we did was run a series of function tests on the controller. The function tests, which can be run either with a VAG-COM or a VAS 5052 diagnostic scan tool, clearly demonstrated that there was nothing whatsoever wrong with the function of the J605 power trunk lid controller. During different phases of the function test, the trunk lid opened, it closed, the latch extended, the latch retracted - in other words, everything worked perfectly.
So - we then decided to have a look at the measured value blocks for controller 46 to determine if the controller was getting a valid signal from the microswitch. We could hear the microswitch making a 'tick' sound every time it was actuated, and my experience with microswitches in aircraft installations is that if they make a sound, they generally work - there is about a 99% correlation between hearing the clicking sound and a properly functioning switch. But... even though we could hear the click, we did not get any response on the diagnostic scan tool indicating that we were pressing the button. This was odd, and led us to suspect that perhaps the switch was not working. We tested all the other switches that relate to trunk operation - the driver door switch, the trunk closing switch, and the New Jersey Escape Handle (a feature found only on NAR vehicles), and noted that the New Jersey Escape Handle didn't work either.
Facts so far:
1) Controller is properly coded, and shows no faults.
2) Trunk slave controller passes all function tests.
3) TWO switches do not report function when MVBs are checked.
The fact that two switches are inoperative is significant. One inoperative switch would be a reasonable finding - this would suggest a defective switch - but finding two inoperative switches raised a red flag. It is unlikely that two different switches would fail at the same time.
We decided to remove the trunk lid inner cover and check for a loose electrical connector. This is a simple task, the method for taking it apart is detailed at this post: Retrofitting an OEM Warning Triangle to theTrunk Lid. Once we had the cover off, we looked at the wiring. Everything was connected, but something just didn't look right - the cable from the back of the VW logo (the trunk lid microswitch) connected directly to the New Jersey Escape Handle, and the two connectors coming out of the main wiring bundle plugged into each other. This didn't seem to make any sense... unless the VW logo microswitch used radio waves or some non-physical method of communicating information to the rest of the car.
Alex's Phaeton was parked right behind my Phaeton in my driveway, so, we popped the inside trunk lid cover off of my Phaeton, and the cause of Alex's problem became apparant: The last person to have serviced Alex's car did not hook up the wiring correctly. The photo below shows what we found when we took the cover off of Alex's trunk lid. Note how the VW logo microswitch wire leads directly to the escape handle microswitch wire, and how the two connectors from the main wiring harness plug into each other.