What is the 62 mile bug? - GreenHybrid

BigPanda · #1 (**permalink**) 03-30-2006, 04:10 PM

Saw some posts in regard to this, but haven't been able to google any info on it. Can anyone fill me in?

Thanks,

BP

ElanC · #2 (**permalink**) 03-30-2006, 04:23 PM

Quote:

Originally Posted by BigPanda

Saw some posts in regard to this, but haven't been able to google any info on it. Can anyone fill me in?

Thanks,

BP

The HCH2 has two trip odometers. It tracks average MPG for each of those odometers, i.e. for the distance you've traveled since the last time you reset the trip odometer. Many people use this, for example, to track their MPG per gas tank.

Many of the HCHs have a bug where the MPG calculation is reset every 62 miles or so, even when the trip odometer itself is not reset. So we cannot correctly track lifetime MPG, or MPG for a tank of gas, or MPG for any trip that is longer than 62 miles.

BigPanda · #3 (**permalink**) 03-30-2006, 04:47 PM

Thanks Elan,

Glad that I don't seem to have this problem.

BP

dshelman · #4 (**permalink**) 03-30-2006, 05:03 PM

Interestingly, 62.14 miles is 100 kilometers.

toast64 · #5 (**permalink**) 03-30-2006, 06:07 PM

Quote:

Originally Posted by dshelman

Interestingly, 62.14 miles is 100 kilometers.

Yeah, I've seen that posted before, but I really don't think that's it. Last weekend I was on the highway and I watched it really closely. I was going about 60 miles per hour, and the display updates every 10 seconds, so I was going about 1/6 mile between updates. It definitely did not change until just after 63 miles by my observation. Anyone seen something different?

ElanC · #6 (**permalink**) 03-30-2006, 07:55 PM

Quote:

Originally Posted by toast64

Yeah, I've seen that posted before, but I really don't think that's it. Last weekend I was on the highway and I watched it really closely. I was going about 60 miles per hour, and the display updates every 10 seconds, so I was going about 1/10 mile between updates. It definitely did not change until just after 63 miles by my observation. Anyone seen something different?

Well, any time you reset the trip odo manually you'll see that it takes a little while for the MPG number to show up. I think that when starting from zero miles it wants to accumulate some data before showing you a number. The same may happen after the bug resets the MPG calculation, which is why there is a delay.

toast64 · #7 (**permalink**) 03-31-2006, 01:16 AM

Quote:

Originally Posted by ElanC

Well, any time you reset the trip odo manually you'll see that it takes a little while for the MPG number to show up. I think that when starting from zero miles it wants to accumulate some data before showing you a number. The same may happen after the bug resets the MPG calculation, which is why there is a delay.

Makes sense. I think I have a way to test this once and for all. I hope to try it tonight. More to come....

Tim · #8 (**permalink**) 04-04-2006, 09:57 AM

Don't know how much this has to do with it, but computers think/speak in binary - 1's and 0's. You can count from 0 to 63 using 6 bits, that is 000000 thru 111111. To get 64, you need a seventh bit (1000000). Often times when computers do goofy things related to math, it happens on the factors of 2 (1, 2, 4, 8, 16, 32, 64...). If the computer - due to a programming error - is only reading the first 6 bits of the mileage data, it would go 0 - 63 then recycle. It could be some other combination as I'm not sure how they'd handle the decimal.

ElanC · #9 (**permalink**) 04-04-2006, 10:51 AM

Quote:

Originally Posted by Tim

Don't know how much this has to do with it, but computers think/speak in binary - 1's and 0's. You can count from 0 to 63 using 6 bits, that is 000000 thru 111111. To get 64, you need a seventh bit (1000000). Often times when computers do goofy things related to math, it happens on the factors of 2 (1, 2, 4, 8, 16, 32, 64...). If the computer - due to a programming error - is only reading the first 6 bits of the mileage data, it would go 0 - 63 then recycle. It could be some other combination as I'm not sure how they'd handle the decimal.

Unlikely because the trip mileage is tracked in tenths of a mile, and the reset definitely happens between 62 and 63 miles.

Casper49 · #10 (**permalink**) 04-04-2006, 10:55 AM

Quote:

Originally Posted by Tim

Don't know how much this has to do with it, but computers think/speak in binary - 1's and 0's. You can count from 0 to 63 using 6 bits, that is 000000 thru 111111. To get 64, you need a seventh bit (1000000). Often times when computers do goofy things related to math, it happens on the factors of 2 (1, 2, 4, 8, 16, 32, 64...). If the computer - due to a programming error - is only reading the first 6 bits of the mileage data, it would go 0 - 63 then recycle. It could be some other combination as I'm not sure how they'd handle the decimal.

You're on the right track here. Back when I was a Real Engineer, I used BCD - binary coded decimal - dedicate 4 bits for each digit.. 0001 0001 would be 11.

But I don't think BCD's are used anymore, rather it is all done in software. So I would guess, cars with this bug has stuck at bit (or faulty overflow operation). Since only some of the cars have this, I would hazard to guess some hardware fault (bad RAM/Flash).