# Uncommanded resetting of the Trip Computer (miles since last fill-up)



## whealy (Nov 15, 2004)

*When does the computer mileage/gas information reset?*

I’ve noted over the past couple of months that my mileage/gas consumption data (long term) has reset at time without my intervention outside of a refuel. For instance, just this past weekend I was down to a half a tank and it was showing that I had driven 5 miles since my last fill-up. We may not get great mileage, but I know we get better than that! I always fill my tank when I get gas. 
So does this reset when a different key (driver) starts the car? I’m chasing this down now to see if it’s the case. Typically my wife does not drive the Phaeton except on rare occasions. However, I have noticed via stereo settings, as I ignore the profile screen when it comes up, that at times, my wife’s key I is the one picked up when we are driving as opposed to mine. Seems strange, but her purse position is probably closer than my left pocket key position. I may have to go so far as to change my habits and move my keys to my right pocket!
Anyway, any advice on the issues would be appreciated. Not sure if I have a service issue or not.


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## spockcat (Jun 5, 2003)

*Re: When does the computer mileage/gas information reset? (whealy)*

In the Touareg, I believe opening the fuel door rests the "since refuel" computer information. But "long term" must be manually reset by using the controls on the steering wheel. I wouldn't be surprised if the Phaeton was the same.


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## whealy (Nov 15, 2004)

I'll recheck to make sure I'm using the correct term with the long term comment. But for clarification, it's the trip data setting where current, last and total (or something like that) are displayed. It's the current and as a result last that keep getting reset.


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## njwiseguy (Jan 7, 2005)

*Re: (whealy)*

power management issue?


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## PanEuropean (Nov 3, 2001)

*Re: When does the computer mileage/gas information reset? (whealy)*

Sounds like two different issues to me - one being the resetting of the fuel consumption info (both 'this tankful' and 'long term'), the other being which key the car recognizes.
You can tell which key the car recognizes by looking at the screen that appears after the legal warning is dismissed. It will usually show the names of the drivers, with a key symbol beside the key that is currently being recognized and used for the purpose of retrieving a driver profile.
It's possible, I suppose, for two different drivers (two different keys) to have different values in the 'long term' mileage log, but I think it is pretty unlikely that the car would calculate different values for the 'since last fillup' information. I don't know what triggers the car to reset the 'since last fillup' values - but, I don't think it is the fuel flap. There is no position sensor on the fuel flap of a Phaeton. My guess (strictly a guess) is that the car looks to see if the fuel quantity, as indicated by the fuel gauge, has increased since the last time the car was powered down, and if it has, it interprets that as proof that fuel has been added.
Good luck with it...
Michael


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## amybeth72 (Jun 23, 2005)

*Re: When does the computer mileage/gas information reset? (whealy)*

So I thought I was the only one who had seen this happen! My trip odometer reset frequently, especially after long road trips. I actually started tracking it to try and figure out what was going on. I never noticed the rest of the stats resetting, but the trip odometer really puzzled me.
Turns out that if I let the odometer go without resetting the trip odometer when I refueled, when the miles travelled would get past 621 miles, the next time I would shut my car off and restart it, the trip odometer would be reset to 0. I actually watched it happen a few times, and finally realized that 621.37 miles is equivalent to 1000 kilometers. So... I'm pretty sure my Phaeton still thinks he's German sometimes.


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## PanEuropean (Nov 3, 2001)

*Re: When does the computer mileage/gas information reset? (amybeth72)*

Hi Amy:
When you refer to the 'trip odometer', do you mean the display in the big Front Information Display and Control Head (between the two front seats), or the display in the instrument cluster (between the speedometer and the tachometer)?
Michael


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## amybeth72 (Jun 23, 2005)

*Re: When does the computer mileage/gas information reset? (PanEuropean)*

Originally I meant the odometer on the dash that you can reset by pushing the 0.0 button (oh I'm so not technical when it comes to what the names of car parts are!)... That's where I noticed the trip odometer resetting itself at first... but, after I saw it happen a few times, I noticed the long term trip settings (as viewed in both the "big Front Info Display" and the "display in the instrument cluster") also reset at the same time. I actually asked about it when I took him in for his 5K, and no one could figure it out. There were no faults detected and all seemed OK. I'm convinced he still thinks he's not in the States and is back in Germany!!!


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## whealy (Nov 15, 2004)

*Re: When does the computer mileage/gas information reset? (whealy)*

Yep, I understand the differences in the profiles and the ability to change them regardless of the key being used. The information I’m asking about is displayed on the information screen that is reached after selecting the Trip Data hard button and the Long Term Data soft button selection on that screen. This displays milage and miles for three categories, Since Refuel, Last and Total. The Since Refuel and as a result Last have been off as they seem to be resetting at inappropriate times. My though to was like Michael’s in that I figured the reset occurred when the sensors determined that fuel had been added. I’m not sure how it handles it if you don’t fill up all the way.
This morning, I drove with my wife’s key and used her profile. That did not reset the Since Refuel, Last numbers. So it would seem that changing the profile does not reset these values. Makes sense to me. I was just chasing this to see if I could find a simple solution to the issue. Looks like this will be added to the 10,000 mile service list. I’ll update if I get any meaning full information on this issue. Seems like most are not experiencing this.


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## njwiseguy (Jan 7, 2005)

*Re: When does the computer mileage/gas information reset? (whealy)*


_Quote, originally posted by *whealy* »_...
Seems like most are not experiencing this.


Definitely not experiencing the issue that you are having. If anything, my "since start" data sometimes does not reset itself even after the car has been left overnight. My "long term data" has never been reset - almost 9,000 miles on it, and the "since refuel" data resets itself perfectly after - well - refueling.


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## car_guy (Aug 19, 2005)

*Re: When does the computer mileage/gas information reset? (njwiseguy)*

My "Since Refuel" stats reset between refuelings once or twice a while ago, but has been behaving better since. Once, when I was in a big rush and put in just a little gas, it didn't reset. I got great mileage that time!


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## calmone (Feb 15, 2006)

*first quirk*

sunday i didn't drive the phaeton, and monday when i got going i noticed that the data for "since refuel" had decided to begin anew even though i had 3/4 of a tank left. also, the "last" column indicated i had gone 100 miles wjen i recalled it was about twice that much.
let's see, if it were imperial gallons..................... NEVER MIND!


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## WISVW (Aug 25, 2003)

*Re: first quirk (calmone)*

My wife's outside thermometer read 136 degree's yesterday! That was 100 degree's hotter than it was. This made the air conditioning go into full blast mode







By the time they got to the mall they were frozen! When they got out and restarted all was well.


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## GripperDon (May 9, 2005)

Resetting by re starting is a wonderful thing like rebooting the home computer.


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## Kcmover (Jul 20, 2005)

*Re: first quirk (WISVW)*

You sure that hot air wasn't inside the car?


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## PanEuropean (Nov 3, 2001)

*Re: first quirk (calmone)*

Hi William:
This topic (fuel consumption on the trip computer suddenly resetting) has come up a few times lately - I'll ask VW if they are aware of a fix for it. I sort of suspect it is an instrument cluster software issue, but that is just an educated guess. Would you please let us know what the last 4 digits of your VIN are, to determine when the car was built? You can replace the last two digits with zeros if you wish (e.g. 8700 series, 6100 series).
Michael


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## WISVW (Aug 25, 2003)

*Re: first quirk (Kcmover)*

Do I tell my wife about that post or not?


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## calmone (Feb 15, 2006)

*Re: first quirk (PanEuropean)*

8106


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## calmone (Feb 15, 2006)

*Re: first quirk (PanEuropean)*

michael, 
did you not say earlier that tsb 05-04 (instrument cluster display distortion) also cures the resetting problem?


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## PanEuropean (Nov 3, 2001)

*Re: first quirk (calmone)*


_Quote, originally posted by *calmone* »_Michael, Did you not say earlier that TB 90-05-04 (instrument cluster display distortion) also cures the resetting problem?

Hi William:
Well - I didn't say it in so many words, but I certainly did imply it.
I don't have it from an absolute authority on the matter (a 'forum friend', so to speak) that flash-updating the Instrument Cluster Controller software (controller 17) solves the uncommanded resetting of the trip computer, however, anecdotal evidence is sure starting to point in that direction.
If it turns out that this is the case, then that is great news for us (and for Volkswagen). The total cost of updating the instrument cluster software is less than $100 - it's labour time only. The total cost of replacing the big display between the two front seats is over $3,000.- So, for everyone's sake, I hope our newest theory that the instrument cluster software update is the solution is, in fact, correct.
As for your vehicle, with the VIN ending with 8106 - that's the same vintage as my Phaeton, which indicates that you have a very early version of the instrument cluster controller software - your software probably ends with the version number x12. The current version ends with x21. Perhaps ask your VW dealer to flash it up to the most current version in accordance with the TB next time you take the car in for service and see if that solves the problem. Because it is such an inexpensive action, I think it is quite reasonable to update it 'on spec', so to speak, and see if that fixes things.
Michael


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## PanEuropean (Nov 3, 2001)

*Re: first quirk (calmone)*

*Archival Note: * _Merged the recent thread "First Quirk" in with an older thread "When does the computer mileage/gas information reset?" and changed the thread title to "Uncommanded resetting of the Trip Computer (miles since last fill-up)" to consolidate all information into the same discussion, and make future searching easier. _ MM
*Also:* Here's a link to the thread that explains what the whole process of updating the software in the instrument cluster is: TB: Distortion in the Display Unit in the Instrument Cluster (MFI, or Y24). The explanation of how the update is carried out is towards the bottom of that thread.


_Modified by PanEuropean at 3:16 PM 3-23-2006_


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