Unreliable Computer Output

[kebleil]

In our first 1200 miles, I have seen some irratic computer output. The dealer is 80 miles away, so I don't want to drive up there and have them tell me - oh, that's just the way it is . . .

So I'm looking for input from other Sonic owners. This is what I've seen.

1. The not all that uncommon inflated mgp - ranging from 2.5 - 8 mpg over actual mpg.

2. I like watching the dashboard mpg reading and particularly attentive to the changes that take place. On 2nd tank of gas, I noticed the the mpg reading was not changing. I drove for another half hour - and still no change. I finally reset the mpg reading and things started to move again.

3. The fuel gauge can be erratic. Today, we were crusing along with 5 bars remaining and suddenly there were only 2 bars. It took about 20 minutes for 2 of the missing bars to return (to 4 bars). Then, when we were accustomed to the 4 bars, suddenly there was only 1 bar, and then gradually the bars returned.

One of the things that attracted me to this car was the computer screen and all the helpful feedback it gives the driver. But if I can't count on it to give me accurate information, what's the point? Is anyone else having issues like this? Do you think I need to take it back to the dealer? Will they have anyway to check to see if it does, indeed, have "issues"? Would like some other's opinions before I trek back to the dealer.

TIA
Kandy in MO

 

[Eric Smit]

Hmm.

1) Not all that uncommon, but 8 is kind of intense.

2) Maybe it was averaged out and you were getting the same MPG as displayed?

3) I'd say sometimes fuel gauges fluctuate, but that seems a little extreme.

I know you don't want to, but it is probably in your best interest to take the car to the dealer. Maybe give them a call and ask the service manager what his or her recommendation is.

Also, erratic.


-Eric Smit

 

[CoHPhasor]

the mpg behavior is normal' without a reset averages wont change quickly.
the fuel level? unless you were on a bad incline the connectin in the fuel setup might be loose/malfunctioning

 

[kebleil]

Thanks Eric. Anyone else want to chime in here?

 

[theenico]

I am just reiterating/repeating what Eric said. With the avg. MPG reading, it will keep averaging from the last time it was reset. The longer you go between resets (regardless of fill ups), the slower it will respond. For fun, hit the reset while coasting in neutral down a long hill.

I have no input for the erratic fuel gauge.

 

[Opticon]

These traits are not typical. You have a problem. Your dealer should not dismiss you.

 

[Steve Dallas]

These traits are not typical. You have a problem. Your dealer should not dismiss you.

1, 3 & 4 are not normal.

2 is absolutely normal. The MPG meter is an average. So, the more you drive, the the more miles you put on, the less it will fluctuate. Remember, it's not an instant mpg meter which shows you the actual mpg at that time.

 

[Opticon]

That is correct. I was focused on the tank level problem and it's possible affect on the MPG accuracy. The gauge readout is heavily buffered and I have never seen my readout fluctuate over even a single bar. To have it drop 4 bars and then recover suggests that a related sensor is malfunctioning.

 

[slimjim550]

In our first 1200 miles, I have seen some irratic computer output. The dealer is 80 miles away, so I don't want to drive up there and have them tell me - oh, that's just the way it is . . .

So I'm looking for input from other Sonic owners. This is what I've seen.

1. The not all that uncommon inflated mgp - ranging from 2.5 - 8 mpg over actual mpg.

2. I like watching the dashboard mpg reading and particularly attentive to the changes that take place. On 2nd tank of gas, I noticed the the mpg reading was not changing. I drove for another half hour - and still no change. I finally reset the mpg reading and things started to move again.

3. The fuel gauge can be erratic. Today, we were crusing along with 5 bars remaining and suddenly there were only 2 bars. It took about 20 minutes for 2 of the missing bars to return (to 4 bars). Then, when we were accustomed to the 4 bars, suddenly there was only 1 bar, and then gradually the bars returned.

One of the things that attracted me to this car was the computer screen and all the helpful feedback it gives the driver. But if I can't count on it to give me accurate information, what's the point? Is anyone else having issues like this? Do you think I need to take it back to the dealer? Will they have anyway to check to see if it does, indeed, have "issues"? Would like some other's opinions before I trek back to the dealer.

TIA
Kandy in MO

1. If you are looking at the "instant MPG" that will change all the time depending on if you are going up hill down hill, how fast you are going ect.

2. as for the average MPG that will depend also on your driving habits as well spread over a long period of time.

3. now for the gas gage that dose not sound right and you may want to have the dealer look at that. Next time you fill up on gas see where the gauge is compared to how much gas it takes to fill up the tank. but remember the gas gage is just an estimate of how much gas you have.

 

[slimjim550]

Now while I have no issues with the readouts that kebleil has I do have a issue with the tire pressure read out in that it dose not give you a tire pressure read. I keep getting in my E mail read outs from on star that I have low tire pressure in all four of my tires but lo and behold nothing on the dash board. On our other car (Cobalt) there is not only a chime for a low tire each tire pressure can be read on the dash no such reading on the Sonic.

 

[Eric Smit]

We can't see the tire pressures. Only a low pressure light. push your Onstar button, say "advisor," wait, say "hello sir/ma'am, can you please tell me my tire pressure?" If they say they can only see the monthly email, tell them to send your the vehicle the diagnostic code.

And if they say they can't do that, ask to speak to a customer care rep and complain, because they not only can, but are supposed to.

now, if onstar can't connect to your vehicle, unplug your Ultra/Scangauge. Still no connection? Ask for customer care and voila.


-Eric Smit

 

[gsxr1000]

The average MPG is very screwy... always reads 2 or so above actually... but the other thing it does is it counts the miles you drive easy (great gas milage) more then when you you bad gas milage... so if you drive careful and at 60 mph for a half tank.. you will be getting 45-50 mpg then other have you drive it like a race car 20-28 mpg... it will read much higher then the mathmatical mpg.... atleast 8 off

 

[Vanye111]

Remember, it's not an instant mpg meter which shows you the actual mpg at that time.

I miss that on my old '01 Dodge Stratus SE. I used to be able to get 34mpg on the highway in that thing, going about 73mpg...

 

[jchasp59]

In our first 1200 miles, I have seen some irratic computer output. The dealer is 80 miles away, so I don't want to drive up there and have them tell me - oh, that's just the way it is . . .

So I'm looking for input from other Sonic owners. This is what I've seen.

1. The not all that uncommon inflated mgp - ranging from 2.5 - 8 mpg over actual mpg.

2. I like watching the dashboard mpg reading and particularly attentive to the changes that take place. On 2nd tank of gas, I noticed the the mpg reading was not changing. I drove for another half hour - and still no change. I finally reset the mpg reading and things started to move again.

3. The fuel gauge can be erratic. Today, we were crusing along with 5 bars remaining and suddenly there were only 2 bars. It took about 20 minutes for 2 of the missing bars to return (to 4 bars). Then, when we were accustomed to the 4 bars, suddenly there was only 1 bar, and then gradually the bars returned.

One of the things that attracted me to this car was the computer screen and all the helpful feedback it gives the driver. But if I can't count on it to give me accurate information, what's the point? Is anyone else having issues like this? Do you think I need to take it back to the dealer? Will they have anyway to check to see if it does, indeed, have "issues"? Would like some other's opinions before I trek back to the dealer.

TIA
Kandy in MO

My trip computer is optimistic, too, and will report 4 to 5 mpg more than my actual mileage. I'm also disappointed that I'm not getting very good gas mileage, and can rarely manage 40mpg on the highway, and only for a short period of time.
Also having a problem with my gas gauge. It'll drop to 3/4 of a tank after about 30 miles, but then seems to act normally. If I fill up a 1/2 tank, it's just over 6 gallons, so I'm thinking that there's a problem with how the fuel level is reported. I also get different fuel levels when comparing the gas gauge and the OnStar Remote Link app on my phone. Beats me how two different values can be reported from the same source.

 

[michalsd]

I must have the only pessimistic sonic out there. My display almost always reads about 1 mpg lower than my calculated mpg.

 

[SooperSonic]

The onboard MPG computer is optimistic by about 2-4MPG's. I reset mine after each fill.

The gas gauge should not make a sudden drop like you said, so I would at least call the dealer's service department and see what their recommendation would be. They will probably say something like it's part of the break-in period and have some patience, but I would push them to get some answers.

 

[LS1notFOUND]

When the low lights come on I have about 2 gallons in reserve, no matter how close to empty I think I get, I seem to put in 10 gallons....the most I've ever put was 11.5 though.

Now how do you all go about manuallly calculating? I just take the miles driven into how much I could fit in the tank at the next fill up.

 

[theenico]

For the most consistency when doing the manual calculation, I refill at the same station and same pump.

I've found that the readout on my car is consistently within 1 MPG of my manual calculations.