I received the new antenna and measured the same resistance on the new one as the old.
I checked the continuity of the two wires going from the KESSY to the R138 antenna. Both wires checked ok. It took me awhile to figure out the numbering of the pins on the T81k connector. I'll give VW the benefit of the doubt that they did put them in right place and the system they used made sense to them.
As I had some spare MOSFETs left over, I had a real electronics guy have a go at replacing them. I checked everything I could find on the board that looked like a fusible resistor. All were ok.
I put everything back together with the new antenna and got the same result...open circuit on the R138 antenna. I checked for DC voltage at the antenna connector and didn't get anything significant.
It looks at though if I want this thing to work I need a new KESSY.
OK, don't start calling me "Mr. messy Kessy" now.
I think there is a fix for this situation. From what I understand of your description of the fault is that everything works after you have cleared the fault. Then, after some driving the Kessy seizes to function with again a 00183 Antenna fault when you scan with VCDS. Clearing that one makes the Kessy functional again, for another limited time period.
It appears that this issue is experienced by Touareg Kessy adventurers as well. One forum member noticed that the R138 antenna fault "disables" the keyless functions. To quote his observation:
"I found that disconnecting the front antenna in the center console stops code R138 from showing. R138 seems to be the "disabling" code."
So the fix is simple. Disconnect R138 antenna and the DTC should not appear again, at least not while driving. Your other antenna's take over full functionality, as the range between your key and any antenna in the car is only very small.
The DTC then will only be generated when you make a scan, not while driving. So if you see this fault after you have made a scan, then simply clear the faults, do not re-scan, close controller and VCDS, which will give you full functionality of your keyless functions.
If you want to read more about this, see this post
Well, after contacting the nearest Phaeton qualified dealer I decided to take one more go at the KESSY as unhooking the R138 antenna didn't solve the problem.
I double checked the six "usual suspect" resistors. All were still ok. Using the Access/Start control module wiring diagram which details the connections to the controller, I measured the resistance across several of the antenna connection pins. The R138 antenna connects at pins 25 and 28. I measured approximately 10k ohms. I also measured the R137 pins (44 and 45) to be less than one ohm. The same measurement for R139 on pins (26 and 27).
Something is definitely different in the circuitry for the R138. I've been trying to follow the traces on the board but it's tedious to say the least without a diagram of the internals of the controller. I'm planning on spending some more time with it tonight.
Perhaps this is Quixotic in nature. When I approached my wife about having the dealer replace it, she asked "is it really worth that much money to be able to open the doors without using the key?"
I checked with a rebuilder of automotive electronics modules and they could do it for about half the cost of the dealer, however; the available information about them didn't inspire confidence. Ideally I'd buy the module from my VW parts source, install it myself in the dealer parking lot and have them program it thus saving the labor for the install. I'm pretty sure they wouldn't go for that seeing as how they didn't install the thing themselves (and would have to push the car into a bay).
Something is puzzling in your observations. The first time you measured R138, it was 8 ohms and now it is 10k? I'm not sure whether you measured on the antenna terminals (Kessy disconnected) or on the corresponding pins of the Kessy.
It is necessary to reverse the polarity of your test pins on every component you are testing, to see if this makes any difference. Diodes in the circuit can cause different readings when the polarity is reversed, so it is very likely that you DO see different ohm readings, depending on polarity of the ohm meter.
And is your DMM equipped with a diode test setting? The test voltage is then cranked up a bit, and the reading then is in Volts. This is easier to identify diodes in a circuit and to test them. Reversing the polarity will give a different reading as well, at least when diodes are in the circuit.
It will be interesting to see what differences you see between the access antenna's.
Sorry for the confusion...it made sense in my head but less so when written out. I measured the R138 antenna itself to be approximately 8 ohms.
Measuring the resistance of the the two terminals (pins 25 and 28) on the KESSY itself yielded a value of approximately 10k ohms. For comparison, I measured the resistance across the appropriate pins for antennas that do not generate fault codes and found it to be less than 1 ohm.
I did not try reversing polarity nor did I try the diode setting. That'll be on the docket for tonight.
As always, I'm most appreciate of your insight.
I'm glad something productive is coming from my series of posts. In the process, I have learned a bit about electronics so I imagine I can count that as productive as well.
I think I'm at the point where I break down and replace the darn thing. The combination of cost and time involved getting the car to a Phaeton-trained dealer have been my motivation to keep pushing on. If one or the other had been less, I'd have had it in to the shop a week or two ago.
I've spent some time with my electronics guy during the past two days going through the board component by component trying to pinpoint a failure. I've found that the resistors are generally ok but there are half a dozen diodes that are suspect. When reverse-biased, they show approximately 1 volt.
I guess much depends upon how enjoyable you find this deductive process - I wouldn't - and I am a duffer when it comes to electrics so it was never on the cards for me to attempt.
Of course if I had been driving through the Netherlands in the kingdom of King Kessy..........
I'm sure his highness will offer his thoughts on the reverse biased values shortly.
KBO as Churchill used to say...
"KESSY" lists at £338.40 + tax, which is not trivial but still a lot less than some controllers. I guess most of the costs are the labour for hooking up to VW HQ to reprogram the security keys [edit - I mean the embedded coding keys in the controllers, as well as the physical door keys].
Last edited by Paximus; 08-07-2012 at 06:52 AM.
I think that Stephen realizes that there is not so much hope left. The only hope I can see, which is the reason to recommend to go to the dealer, is that the dealer finds another cause, previously overlooked. Perhaps some other component is defective, and there is some hope that the Guided Fault Finding function of the dealer’s VAS system points into the direction of the real cause of the problem. It sure is not impossible that the KESSY has some other defects and that it DOES need replacement. But I don’t think that much brass can be saved by buying the KESSY somewhere else, because there is some risk that the dealer will refuse to program it. Or charge double because of the “extra work”, in other words, a Yorkshireman surcharge.
Perhaps the most important reason to ask the dealer to handle it, is that what originally started as a fun job, appears to have turned into a nuisance. Then the answer to this question:
is more easy to answer. Let there will be hope again.I'm planning on spending some more time with it tonight….
When I approached my wife about having the dealer replace it, she asked "is it really worth that much money to be able to open the doors without using the key?"
Yes, I've raised the white flag. I have an appointment at the dealer for a replacement in 10 days or so. Although I'm not a Yorkshireman, it pains me about as much, however; my long term plans for the car include the keyless start button and I don't think it will work if the KESSY isn't 100%.
I'll report back on my results!
There is, without question, a frisson of pleasure for me every time I approach the car and it unlocks automatically - another follows very shortly afterwards when I place my foot on the brake and press the stat button.
Women do not understand these things - my wife questions this with me in exactly the same way.
I am passed my mid-fifties - I need as many instances of frisson that I can get!
As Willem wrote, i think you are wise to surrender - the fact that my dealer said that to get the new Kessy all working was the most complicated thing they have ever don on a VW gives some indication of what you are up against - they were on the phone the best part of 3 hours with VW Paris!
Still well done, Quitters never win and all that................
An update to my continuing saga:
I had the car in to the dealer several weeks ago to have them replace the KESSY module. When they brought the car round from the back, I tried the keyless entry functions and got the same result as before. The trunk will open via the push-button VW emblem, however; the doors will not unlock or lock using the keyless functions.
I left the car with them and they agreed to look into it some more. The next day, they called to say that they had it working. According to the service adviser, it was a software setting that needed to be changed. I asked them to take the car for a drive cycle and see if it worked afterwards. They called back and said that, no it was not working. This is consistent with the behavior I have observed previously. I asked that they spend more time troubleshooting which they agreed to do at a reduced labor rate.
The technician found faults for the R138 interior antenna and the R136 rear antenna behind the bumper cover. The explanation I was given was that the antennas were picking up noise or static I told them that I had replaced the R138 antenna and had checked the wiring, finding it satisfactory. The technician confirmed my findings on the R138 antenna and found the resistance on the R136 antenna to be too high. They recommended replacing the two individual antennas that constitute the R136. I did this myself this afternoon and it didn't solve the problem. VCDS reports open circuit faults on both the R138 and R136 antenna after either going through a drive cycle or scanning the KESSY controller. If I clear the codes and leave it alone --no driving or rescanning-- the keyless access will work.
I'll make one last plea for help and wisdom before I give up. What could possibly be causing these faults? Why does the trunk work when nothing else does? There are no other non-intermittent codes on other controllers.
Perhaps the technician was referring to "coding"? Your original coding was 0137452. When a controller is not responding well, it can be restored to factory settings by entering the same code again and then press "Do it!" This defaults all previous adaptations (beeps and whistles, door locking and unlocking behaviour etc.) to factory standards. When your dealer tried this, and all suspect antenna's were already replaced, then a new Kessy is the only way to glory.According to the service adviser, it was a software setting that needed to be changed.
Archival Note: Related discussions, listed in Forum TOC -
Repairing the Access and Start Controller (controller 07) - resolving antenna 'open circuit' faults
Kessy and Keyless Access discussion
Please don't send me technical questions via IM - instead, post your questions onto the end of the most appropriate thread in the FAQ, so that everyone can benefit from the answer, and everyone can assist in providing the answer. Thanks, Michael
Yes, they did replace the KESSY with a new one. I replaced the rear antennas myself with new ones. I was absolutely sure that a new module would fix the problem...so much so that I was willing to lay out the cash to have it done. I will try recoding it with the original coding this evening and hopefully will have a chance to check the wiring from the rear antennas to the KESSY connector this weekend. I'm going to need some long multimeter leads!
Last edited by StevenFT; 10-04-2012 at 06:56 PM.
Sorry to hear that this is still unsolved.
I have no specific wisdom to offer as to cause but the comment of my Phaeton tech after he replaced my Kessy comes back to me: "It took us almost 3 hours on the phone with VW Paris to code the new Kessy, it was the most complicated thing I have ever done".
In other words, there's a lot of potential for error so maybe insist that they go over it all again.
To say that my heart sank when I went to pick up the car the first time doesn't come close to describing how I felt. According to the invoice, it took the technician 3 hours to complete the job. I imagine a lot of that was time on the phone as it only takes 20 minutes to do the physical labor.
The tech spent another two hours troubleshooting the antennas. If I do eventually find the cause of the faults, I bet it'll be something simple but very obscure.
Thanks for the sympathy...
This is nerve wrecking...But it is also not very good for the reputation of VW not to find the cause of this problem. Perhaps you can ask you dealer to do a little more efforts to find the problem. What they might want to do is to consult higher authorities, accurately describing what they have replaced and tweaked so far. My guess is that there should be at least one expert available (perhaps in Dresden) who has seen this problem before.
Additional details, such as the rather low ohm values you found (and the strangely high readings which the technician found), may help in the problem solving process.
But is looks like the repair job of your original Kessy was done correctly. It is at least as good as the new one!