VW's "VagCom" is just their own version of a scan tool. I've never had one in my hands so I don't know exactly how much it really does. FWIW, I'll never own one either. I do have a VeDis scan tool which is one of the strongest aftermarket European scan tools available but it is still an aftermarket tool, and I just don't expect it to be 100% complete. But it's the best I can afford. (5K+ there are others that are over a $20K investment, they do more than my VeDis, but imagine spending that kind of money and in a years time not expect to even get $1000 in diagnostic labor money back while using it) It's really tough fixing cars these days when it comes to tooling and equipment. I can justify (to a degree) owning O.E. tools for some 90% of the market. (GM, Toyota, Ford, Chrysler, current model years and Honda through 2004) But even with Honda I cannot justify staying current with the O.E. tool, because at $9,000 for just Honda's since 2005 I don't see enough of them to justify any greater expense in supporting them than whatever I can get through my VeDis Asian, or Snap-On scanners. But back to doing the diagnostics on this TAC problem. Even the VagCom does not actually tell the tech what is wrong. The cars are not sophisticated enough to do that. When a problem is determined by the system, say an open in one of the circuits. The system is good enough to flag the circuit affected, and in some cases might have a code that is accurate enough to say that the circuit was "open", although most of the time it will be more like circuit open/short. The problem with intermittents is the circuit is going open/short at any point through that entire single circuit, but the diagnostic system is not capable of saying where it occured. Likewise a scan tool, displaying serial data will show what the microprocessor shows that a particular sensor circuit is reporting, but it's up to a technician to figure out exactly why a given sensor is reporting incorrectly when/if it is. Many events we deal with have a circuit that has a problem, the computer stores a code, but the circuit then just happens to operate correctly when the vehicle comes in, and we end up in a no-problem found situation. redpennies car at this point appears to provide a challenge to any technician because it is not broken all of the time. Combine that with her frustration from the expense of both related (potentially) and unrelated repairs and the fact that in a flat rate shop the techs quite often don't get paid correctly to take whatever time is required to get it to act up and diagnose it and you have a perfect example of just what fixing cars can be like for a technician as well as the public. In every real sense, my getting involved with any of these threads is time spent at work, that I don't get paid for. The techs at the VW dealership when they work on her car now in all likelyhood don't get paid for their time either unless they can justify replacing some part, that redpenny pays to have replaced. It looks like such great customer service to not pay anything to a customer when they have a complaint, but it's actually decades of a robbing Peter to pay Paul situation. The price of which is starting to finally become obvious. Could I diagnose and fix red's car. Yep, no doubt. Would she really be happy if I did? Hard to say......

I had the orginal battery still in my car they said with this car it has to be put on the computer to conform to the engine???????????????????? I'm not quite sure what they mean by that, except that there are some settings on the car (like whether the alarm horn beeps, the radio can be used, and some others) which can be set by computer but which may default to factory-standard if the battery dies. But the important thing is that they finally fixed it for less than another fortune. Please keep that dealership/garage in mind for your future maintenance. You definitely want to keep track of competent technicians!

Call or visit the dealer they may have a front tag accessory kit and/or tell you where you will find some hidden holes already there for mounting it.

Issues like this cannot always be accurately explained in a "silver bullet" answer. The alarm lamp, and the issues with the door locks do suggest that a common failure with the drivers door wiring harness "might" be occurring but starting the diagnostics expecting to find that is a tactical mistake that I call "Tainted Intuition". You need a properly trained technician with the correct tool a VAG-COM, or preferably VAG5052 which would give the technician the ability to communicate with the body, immobilizer and door modules. BTW, I don't agree with the assumption that the check engine light being on won't hurt anything. Your number one warning should another failure begin to occur would the the Check Engine light getting turned on. With the lamp already on, and obviously a hard code set you lose that warning because of course the light is already on. When the lamp is on, it means the car is suspected of polluting the air at least 1.5 times the FTP testing limit that the vehicle is certified to. The tendency for owners to ignore the lamp is the primary cause for active emissions testing in many states. Finally once the car noticeably runs bad and you finally decide to have it fixed, exactly where would you expect a technician to accurately start and stop the repair? You could have any number of active failures by then, and who knows how many blocked tests have failed to run because of the active failures. Replacing the PCM would not cost $1300 all by itself, what else did they say the car needed?