# Car fuel economy meter counts backwards **URL:** \ **Category:** Maintenance/Repairs\ **Created:** [March 29, 2020, 9:43am UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038 "2020-03-29T09:43:36Z")\ **Posts on this page:** 17\ **Page:** 1
**Author:** ![Kasper-Lu](https://avatars.discourse-cdn.com/v4/letter/k/e8c25b/32.png) [@Kasper-Lu](https://community.cartalk.com/u/Kasper-Lu)\ **Post date:** [March 29, 2020, 9:43am UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/1 "2020-03-29T09:43:36Z")
Hello there, I would like to ask, after I have changed a new battery my car electronic live fuel consumption meter runs backwards. Example, max live fuel consumption is 30.0 L (if i press gas pedal to ground in first gear) and when I drive normally in 5th gear its 5.5 L. But now it show in reverse, when I drive normally in 5th gear its 24.5 L. And when I speed in 1st gear its 0 L or 0.5 L. … It seems values in car computer got reversed? I have Opel Agila B 2009 or Suzuki Splash \*same cars Anyone with some experience in this? Kindly, Kasper ---
**Author:** ![COROLLAGUY1](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/corollaguy1/32/7575_2.png) [@COROLLAGUY1](https://community.cartalk.com/u/COROLLAGUY1)\ **Post date:** [March 29, 2020, 10:51am UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/2 "2020-03-29T10:51:14Z")
Yes,it doesn’t make sense. You probably fried something when you installed the new battery. It looks like the polarity is reversed. ---
**Author:** ![texases](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/texases/32/862_2.png) [@texases](https://community.cartalk.com/u/texases)\ **Post date:** [March 29, 2020, 11:29am UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/3 "2020-03-29T11:29:43Z")
Could it have switched to miles per gallon? ---
**Author:** ![Kasper-Lu](https://avatars.discourse-cdn.com/v4/letter/k/e8c25b/32.png) [@Kasper-Lu](https://community.cartalk.com/u/Kasper-Lu)\ **Post date:** [March 29, 2020, 12:19pm UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/4 "2020-03-29T12:19:19Z")
Thanks for replies. I think, I might have touched jump start cables together… when the battery was dead. All the rest in the car computer works fine. Just fuel consumption meter polarity has reversed… wow 😃 Hmmm… is it costly to fix? Do I need to change whole sensor or? ---
**Author:** ![common-sense-answer](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/common-sense-answer/32/716_2.png) [@common-sense-answer](https://community.cartalk.com/u/common-sense-answer)\ **Post date:** [March 29, 2020, 12:38pm UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/5 "2020-03-29T12:38:25Z")
> [@Kasper\_Lu](#): > > I think, I might have touched jump start cables together… Is _“I think, I might have touched jump start cables together…”_, the same as _“I seem to recall touching the cables together”_, or, _“I did touch the cables together”_ ? 🤨 **How long ago did you change the battery and possibly initiate this problem?** The reason I ask is I’d be afraid that something else besides that economy meter could have been damaged. Carefully monitor for other anomalies. Obviously (or not), “modern” cars have sensitive electronics and great care must be taken when working with battery cables. _ **CSA** _ 🌴 🕶 🌴 ---
**Author:** ![VDCdriver](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/vdcdriver/32/48514_2.png) [@VDCdriver](https://community.cartalk.com/u/VDCdriver)\ **Post date:** [March 29, 2020, 12:49pm UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/6 "2020-03-29T12:49:45Z")
> [@Kasper\_Lu](#): > > All the rest in the car computer works fine. While a fuel economy meter is a nice feature to have, I would advise that you not waste your money on repairing this problem with your 11 year old car. That money would be much better-spent on scheduled maintenance, and on repairs that might be needed in the _vital_ areas of the car. ---
**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\ **Post date:** [March 29, 2020, 12:50pm UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/7 "2020-03-29T12:50:56Z")
I’m betting the algorithm is maxing out on highest consumption due to the values getting reset when power was lost. The normally low amount is high. Which it would be without long term averaging. The highest consumption rate is probably out of range and that’s why it looks goofy. A lousy implementation if that’s happening. Just give it some time to develop long term averaging… ---
**Author:** ![Mustangman](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/mustangman/32/44130_2.png) [@Mustangman](https://community.cartalk.com/u/Mustangman)\ **Post date:** [March 29, 2020, 12:58pm UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/8 "2020-03-29T12:58:39Z")
I think @texases has the correct answer. Check your owners manual, it may well be reading mpg or mpkm instead of L/100km ---
**Author:** ![Kasper-Lu](https://avatars.discourse-cdn.com/v4/letter/k/e8c25b/32.png) [@Kasper-Lu](https://community.cartalk.com/u/Kasper-Lu)\ **Post date:** [March 29, 2020, 1:06pm UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/9 "2020-03-29T13:06:02Z")
Yesterday, old battery died, hooked up jump-start cables and touched them, small spark came out. Started the car and drove out the buy a new battery. Changed it and the problem appeared. Seems that everything works fine, just the live counting values are in reverse, the values are realistic tho, just from the other end. Not in L/miles that is for sure. Because, after 30 min of driving, it counts Average Consumption as 25 l/100 km for a 1.0 engine car. Usually average is 5.0L/100km. hahaha It is just weird that shouldn’t it blow up the fuse in first place? NOT make the sensor work backwards? 😃 I hope I won’t have to change whole ECU. Thanks for replies! I will post if I get news ---
**Author:** ![Kasper-Lu](https://avatars.discourse-cdn.com/v4/letter/k/e8c25b/32.png) [@Kasper-Lu](https://community.cartalk.com/u/Kasper-Lu)\ **Post date:** [March 29, 2020, 1:07pm UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/10 "2020-03-29T13:07:03Z")
Exactly. The normally low amount is high. As if the algorithm has reversed… ---
**Author:** ![Kasper-Lu](https://avatars.discourse-cdn.com/v4/letter/k/e8c25b/32.png) [@Kasper-Lu](https://community.cartalk.com/u/Kasper-Lu)\ **Post date:** [March 29, 2020, 1:08pm UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/11 "2020-03-29T13:08:41Z")
Actually, you are right. I just need to read it in reverse… 25L is 5L and etc. hahaha ---
**Author:** ![TwinTurbo](https://avatars.discourse-cdn.com/v4/letter/t/8baadc/32.png) [@TwinTurbo](https://community.cartalk.com/u/TwinTurbo)\ **Post date:** [March 29, 2020, 1:44pm UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/12 "2020-03-29T13:44:02Z")
I don’t think it’s reversed. ---
**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\ **Post date:** [March 29, 2020, 2:44pm UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/13 "2020-03-29T14:44:37Z")
Both of our vehicles show several things - Temperature - Miles to Empty - Avg speed - Avg Miles per gallon - current mpg . Temp and Miles to Empty are the only ones I care about . The current used goes up and down so much to be useless. ---
**Author:** ![common-sense-answer](https://sea1.discourse-cdn.com/cartalk/user_avatar/community.cartalk.com/common-sense-answer/32/716_2.png) [@common-sense-answer](https://community.cartalk.com/u/common-sense-answer)\ **Post date:** [March 29, 2020, 2:52pm UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/14 "2020-03-29T14:52:44Z")
> [@VOLVO\_V70](#): > > Both of our vehicles show several things - Temperature - Miles to Empty - Avg speed - Avg Miles per gallon - current mpg . Temp and Miles to Empty are the only ones I care about . The current used goes up and down so much to be useless. I hear you. I think I’ve got that crap on some of our cars, too, but it’s all useless to me, like so many other things added to cars. None of it helps me while driving. _ **CSA** _ 🌴 🕶 🌴 ---
**Author:** ![Kasper-Lu](https://avatars.discourse-cdn.com/v4/letter/k/e8c25b/32.png) [@Kasper-Lu](https://community.cartalk.com/u/Kasper-Lu)\ **Post date:** [March 29, 2020, 4:11pm UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/16 "2020-03-29T16:11:18Z")
> [@VOLVO\_V70](#): > > Miles to Empty I see your point. But aren’t Miles to Empty are influenced by Avg Miles per gallon and current mpg? In my case it makes Miles to Empty useless 🙂 ---
**Author:** ![VOLVO-V70](https://avatars.discourse-cdn.com/v4/letter/v/8e8cbc/32.png) [@VOLVO-V70](https://community.cartalk.com/u/VOLVO-V70)\ **Post date:** [March 29, 2020, 4:16pm UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/17 "2020-03-29T16:16:53Z")
Just because you have 1/2 tank left you don’t really know how far you can go . The miles to empty does a very good job of correcting the estimate as your driving pattern changes. Of course like other people I never let my tank get below 1/2 full. Have you not noticed that the avg mpg can change if you return to stop and go from highway driving . Do you not reset with each fillup ? ---
**Author:** ![Kasper-Lu](https://avatars.discourse-cdn.com/v4/letter/k/e8c25b/32.png) [@Kasper-Lu](https://community.cartalk.com/u/Kasper-Lu)\ **Post date:** [March 30, 2020, 11:25am UTC](https://community.cartalk.com/t/car-fuel-economy-meter-counts-backwards/162038/18 "2020-03-30T11:25:47Z")
Today I took the car for a 20 min ride and everything went back to normal. Funny problem. Thanks for support guys 🙂