Odometer Changed miles by it self - 986 Forum - The Community for Porsche Boxster & Cayman Owners

HI has anyone ever heard of the odometer changing miles at random. I have a 1998 base boxster it had 74000 miles on it and it has 2500 hours on the computer which is about right. I disconnect my battery all the time because i only use it on nice cool days with the top down. I had to replace a window regulator so i connected the battery and moved it out side. disconnected the battery and replaced the regulator. reconnected the battery and took it for a ride and noticed that the miles changed to 104000 plus miles? is there a way to change it back to 74000 or am i stuck.... can anyone help or know a way to change it back? I also have a Durametic diagnostic tool There’s no way to change it from kilometers to miles in the software

1st, why are you disconnecting the battery all the time? Really not saving anything by doing that, or even removing it. Sure the cluster didn't revert to KM instead of miles?

74,000 miles would be more like 119, 000 km.

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Regardless, constantly disconnecting the battery is not a good idea on any modern car.

Only because it may be sometimes a month before I go out and start the car that’s why I disconnect the battery. The thing about it is I can change it to kilometers by turning the dial but then it goes to like 150000 whatever it is from 107567. I was wondering if it’s possible that someone had tried to turn back the odometer because I bought it with 69000 four years ago. If you take 2500 hours which is what I have on the motor and I had that checked times an average of 30 mph it’s still only 75,000 miles. I think there’s a glitch in the eprom of the Odometer

Try getting a battery maintainer, even a solar powered one if necessary; your car will thank you......

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I agree!...

I have gone 6 months without starting mine before and didn't have any issues with it turning over the 1st time. Battery maintainer would be much better at a minimum but no matter what, no reason to disconnect it. Miles are stored in the cluster itself and there is no way to re-program them once they are set. Someone with a PST may try to, but I think it will fail anyway. Dont see how anyone could even try to roll it back.

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Well that’s good news, I wasn’t sure if someone had tried to roll it back before I bought it. I don’t know how an odometer can just add miles. Maybe I can write to Porsche in Germany. Of course they mostly would not care about that problem. Funny part is I have listed that car for sale on FB two weeks prior with pictures of the odometer with 74980 miles. Hopefully someone will read this and know a way to fix it…

I've had something similar happen after disconnecting the battery for maintenance, it was pretty shocking to see my 986 suddenly had 0 miles on it. It's happened to a few other people if you hunt through old posts. If I recall correctly the fix is to disconnect the battery, insert the key and turn it to the first position, then reconnect the battery. I have no idea why it works, but it does fix it. Alternately, disconnect the battery and wait a few minutes, repeat, until it reverts back to the correct mileage.

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Thank you so much…..that makes total sense to me. With me disconnect the battery all the time I’m sure I’ve turn the key and then connected the battery not realizing that that would do anything. So thank you so much for the help. If it works… I’ll repost for everyone to know it worked. Thanks again!!!!

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No that did not work…but thank you for the help. I tried about eight times nothing changed. I believe I’m just stuck with it…lol it’s still a great and lots of fun little car to drive. I may take it to a garage and see if they know how to return it to the original miles. I wish I would’ve had to go your way back to zero…lol

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I have been removing the battery for the winter and charging it at home every couple of months because the car is stored in an unheated building. I am ultra conscious about leaving unattended things plugged in throughout the winter, so I don't want a trickle charger on it. I don't want to risk burning my airplane and hangar down just to be kind to a $150 battery in my Boxster. Should I not be removing my battery? This practice seems to be working well for my battery as it is 7 years old and still strong.

For years, we provided winter storage for special customer's cars, which included battery maintainers (not cheap trickle chargers, but a high quality Ctek electronically controlled true maintainer systems, which are both internally and externally fused), as well as for my personal "fleet" in an environmentally controlled and highly secured facility. In all the years we did this, we never had any problems with any of the cars, many of which were with us typically from mid-October until late March. The "secret" is the battery maintainer, which brings the battery up to full charge, then shuts down until it detects the battery dropping off, when it comes back on to top off the charge again before shutting down again. One of the things that show how effective these systems are is in the fact that we top off every flooded battery with distilled water before the car goes into extended storage, and nearly six months later, it still does not need any water. I have personally stored cars for over a year without starting them, and they all came to life instantly when it was time for them to come out of storage. Use quality maintainers, and you will not have any issues. I have also run AGM batteries this way, and often gotten 10-12 years out of them before they started to show drop off during annual load testing, indicating that while they still worked, it was time to replace them. The problem with disconnecting or removing the battery is not what it does to the battery, but what it does to the vehicle, which can be both difficult and expensive. The car simply does not like it.

Neither does your back. If you are going to keep doing it, just disconnect the positive & neg posts but leave it in the car. Ctek maintainers are some of the best you can get. It isn't much different then the Chief I have on my Piper.