I did take down all those numbers, I'm actually used to doing that anyway, and thanks for the heads up on that one. I didn't mean to reset the whole thing - my bad I know, I was just trying for the MPG reading.

I don't think you're "slamming" me at all, I fully acknowledge that I'm not aware of my car's characteristics. And since having these issues I did begin to read the manual from cover to cover. I know I seem like a dimwit, I'm really not, just a first time Chevy owner (well, first time American car owner in general) and have only had the thing for a short time. Thanks very much for reading/replying, I really do appreciate it.

 

I completely agree with you on the CEL issue, but I've been told by multiple dealers that they can't do anything under warranty without the CEL being on, if it is a ECM/BCM issue they won't cover it without an CEL. At least that's what I've come to understand from them.
Thanks for the advice.

 

welcome to the site regardless. I have over 160,000 relatively trouble free miles. Does sound like computer to me as well.

 

I have had very few problems with my 2007 HHR LS. Within a month or two of purchasing it brand-new, I started getting "engine power reduced" messages in the DIC, which was a serious and annoying problem, and it generated DTC codes, but there was never a CEL illumination. The problem was in the wiring harness and it got fixed at the dealer. No trouble since then.

So...I can assure you that you can experience problems with your vehicle without the CEL ever being involved.

As for mileage - the fuel injectors inject a precise amount of fuel into the combustion chamber each and every time they are pulsed. It is trivially easy to totalize the amount of fuel that is consumed while the engine is running. Likewise, it is not difficult to tally up the distance the vehicle has traveled provided that the diameter of the installed wheel and tire combo has not departed from the diameter that left the factory. The MPG you see in the DIC is how much fuel was consumed to travel "X" distance, and includes all time not moving when the engine is running. Ethanol kills advertised mileage.

I can eke out 20 MPG in my bone-stock LS if I include a little bit of highway driving. But when taking a long road trip, I can get 36 MPG in any ambient temperature condition as long as the road surface is dry.

 

No the CEL will not come on typically for a faulty sending unit as the unit sends a resistance value to the computer. So even when it is acting up it will still send some measure of resistance to the computer. The computer does not know a good value from a bad value as long as the value is within the expected range. Like I said this was common in earlier GM's up to 05 as that was when I stopped working on GM's specifically. It was most common to the N and J body cars which the Cobalt/G5 replaced the J body cars and this car is based off the Cobalt. That is why I mentioned it. But the instant MPG also being and issue is why I also suggested the possibility of the computers program.

To reset the MPG only you just need to be displaying the MPG and then hold down the reset arrow button. This will rest ONLY the item displayed which in this case would be the MPG. Now if you go into the programming mode I believe you can do a blanket reset of all params but why would you want to do that lol.

 

Does your low fuel message come up before you run out? That appears every time you start (I have a 2010) and you have two gallons of gas left (about 50 miles for me).