Case study: 2013 VW Phaeton automatic tailgate malfunction – AKA Tales from the nonfunctional crypt BY GARETH DAVIES CAE AMIMI, DIRECTOR EURO PERFORMANCE
A few months ago, one of our local independent garages got in touch seeking advice regarding a VW Phaeton Automatic tailgate. They talked me through the symptoms and repairs that had been carried out and we agreed the best course of action would be for us to take a look and clarify whether a basic setting or initialization was required, or whether the problem resided deeper. Our simple evaluation process began. The first step was to capture as clear an understanding of the customer’s original complaint and ANY relevant information, such as timelines and behavior patterns, to ascertain what testing and repairs (if any) had been carried out to date and to establish a budget for our investigations before updating with my findings. Acquisition data complete, I got the vehicle in to take a look. Initially, I began with a Full Diagnostic trouble code report with a scan tool and a brief observational walkaround to check for any ‘stand out’ details. I decided, given the high specification of the vehicle in question, that I’d go straight in with the manufacturer diagnostic tool, ODIS. I knew that this would be information-rich with diagrams and schematics relevant to this vehicle, and if the nature of the fault depicted a handshake or ‘teach in’ was required, the tool would reduce ‘faffing time’.
CASE STUDY
After reviewing the diagnostic report, I took some time to analyse the stored DTC’s, the job notes acquired and the work previously carried out by the independent garage. I find this stage can be the difference between becoming lost in a diagnostic job and making good efficiency. It’s a great settler to draw patterns between the reported symptoms and what the car is logging in terms of faults, before getting lost in a set of tests, which may, or may not, be relevant to ascertaining the fault/fix.
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Customer reported issues: Tailgate has no functionality, tailgate showing as open on driver information display. Tests or repairs carried out: Forced entry to boot via created access panel in rear bulkhead, boot lock damaged to open boot, chaffed wiring harness found and repaired with new full genuine tailgate loom, new boot lock mechanism/ motor replaced but after test fit, removed as no functionality restored even after these repairs.
Looking at the report, there were a cluster of faults all reporting problems with the rear lid central locking motor (plausible, as the old damaged one was connected for fear of damaging the new 650 VW item), but other than that, the car appeared reasonably well. The report also showed some DTC’s that at face value, were not likely to be relevant to the issue. I didn’t want to waste time on these at this stage. A quick inspection revealed a competent at ‘face value’ wiring repair, and the car had been left in a stripped state to assist with our investigation. After pulling up the wiring diagram, various key suspects were found on the diagram and a basic test plan (of my own, rather than AI on ODIS) was created having familiarized myself with the layout of the system. Which, interestingly, is significantly different on the Phaeton, compared to more common visitors from the Audi Avant Fraternity with ‘Deck Lid Control’, that we see a fair volume of in a faulty state. What did I need to validate? What needed to be working that wasn’t? Where do the instructions for these functions come from? I began testing by establishing whether I had any functionality, by any means, of trying to operate the tailgate – which can be done via the keys, the switch in the driver’s door card, the button to close the lid mounted internally in the tailgate (it was open as the previous garage had forced entry), and the emergency key switch within the rear badge. No method of operation yielded any functionality. My next test was to try and execute output function via the diagnostic tool. This made for the first interesting observation. The wiring diagram and workshop manual referred to a separate rear lid control unit