What does programming the VIN into the ECM do?


#1

We have a 2006 Pontiac Vibe FWD base, now just over 100,000 miles on it. Horrible gas mileage of usually 23 MPG in town, on the highway, or mixed driving. Best we have ever seen is 26 or 27 in the past 18 months that we’ve had the car, and that’s only about 4 times!
We’ve cleaned MAF, put in K&N filter, inflated the Pirelli 17" tires to their max, put in a new O2 sensor and the mileage has not budged. We checked overdrive off and on and the RPM is lower with it on (default) so we think it must be working OK. Fuel mixture does not seem overly rich or lean. Car runs fine and very little pressure is needed on the pedal to get it moving. No codes on OBD-II reader. We have been stumped trying to figure out how to increase the gas mileage.
Last thing we have tried is a new ECM we bought online. Recall did not apply to our car since the numbers on the old ECM allegedly indicated nothing was wrong with the part. New ECM went in easily and the car seems to be running at a lower RPM with it. The CEL is on and the code indicates VIN needs to be programmed into it. No other codes and the car runs great.
We’ve read the threads where people had to tow their vehicles in to the dealer to get VIN reprogrammed, but ours runs without a problem except that we are still getting just 23 mpg. So, I’d like to know whether programming the VIN in will do anything for the car, in particular, will it do anything to improve gas mileage?


#2

The '06 Vibe is rated at 22 city, 25 combined, and 29 highway.
Fixing this is going to be frustrating… 'cause it ain’t broke! Keep trying to fix it, and eventually it just MIGHT be broke.


#3

Here’s what other Vibe owners are getting for mpg:

http://www.fuelly.com/car/pontiac/vibe/2006

As TSM said, it looks like your mpg is normal.

And by the way, the oil on a K&N filter can contaminate the MAF and eventually cause it to give false readings that will reduce your mpg…stock filters are there for a reason.


#4

Rated at 22 city, getting 23, and complaining the mileage is horrible? Wow.

Even if the vehicle was rated at 25 or better a few MPG is easily explainable by fuel formulation, climate conditions, and the always present driver’s foot.


#5

" inflated the Pirelli 17" tires to their max",
I hope you mean the recommended maximum pressure on the door pillar and not the maximum pressure on the tire sidewall. If you exceed the auto manufacturer’s recommendation for tire pressure, you are endangering yourself, your passengers and other motorists on the road.
My only recommendation is to be certain the thermostat is allowing the engine to reach normal operating temperature and is not stuck open so that the engine runs cold. Take a look at your temperature gauge after the engine has warmed up.


#6

I think you have unrealistic expectations for the fuel economy of this car. With the automatic, this car is epa rated 22 city , 25 combined, and 29 highway. That is on the epa drive cycle and no one drives like that. You can probably hit those numbers if you don’t idle your car, you must accelerate slowly, hold your top speed down, anticipate lights and use your brakes as little as possible. Also these are summer numbers only, engines get horrible mileage until they are at operating temp.


#7

Another vote for your mileage being perfectly normal, not “horrible” as you say. Where on earth did you get the idea that 23 is so bad? Out of 4 cars I own only one will get better than 23 on the highway.

If you want mileage, buy an early 90’s Geo Metro.

Programming the VIN into the ECM lets the CAN (Controller Area Network) know that all the modules on the car are online and talking to each other. A mismatched VIN may limit certain safety or convenience features on the car.

As a mechanic, I advise you to remove the K&N and replace it with the stock original filter.


#8

Not an expert about the VIN thing, but remember there’s several computers in the car, and they need to talk to each other. In order to facilitate unambiguous communication, they want to be sure they are all speaking the same language about the same car, so the software designers probably put in the VIN as part of the identification protocol for the communications. When one computer receives a message from another computer and it doesn’t have the same VIN as itself, it is just saying something appears to be wrong with the basic configuration. It may still work ok though.

There’s at least one other VIN objective too, the security system might want to detect if some module or another was removed and replaced with another in order to steal the car or open the doors without the owner’s permission.

Do you have the old ECM? If so, I’d be inclined to just put the old one back in. You don’t want that light on all the time as it will mask actual problems which might need immediate att’n for safety.


#9

I’ll reply to all in this message.

The '06 Vibe is rated at 22 city, 25 combined, and 29 highway.
We were told we’d get 29 city and 34 highway on this automatic when we bought it. I know I’ve seen owners on this forum brag about getting that and more. We would love to see 25 combined or 29 highway instead of the 23 we always get!

And by the way, the oil on a K&N filter can contaminate the MAF and eventually cause it to give false readings that will redice your mpg…stock filters are there for a reason.
We put in the new filter since we also saw owners claim better mileage and performance.
Nothing we have done has decreased mileage but no increase either!

Even if the vehicle was rated at 25 or better a few MPG is easily explainable by fuel formulation, climate conditions, and the always present driver’s foot.
We get the same 23 no matter fuel, climate or the gentle foot of this driver. I got 24-26 mpg on a 1000 mile trip in my 1995 Lincoln Town Car two months ago. Compare 23 in the Vibe.

I hope you mean the recommended maximum pressure on the door pillar and not the maximum pressure on the tire sidewall.
Yes, of course we inflated to what’s on the door.

Take a look at your temperature gauge after the engine has warmed up.
It’s OK. Halfway between cold and hot.

You can probably hit those numbers if you don’t idle your car, you must accelerate slowly, hold your top speed down, anticipate lights and use your brakes as little as possible. Also these are summer numbers only, engines get horrible mileage until they are at operating temp.
Well, I don’t idle, I do accelerate slowly, don’t drive over the speed limit, coast to the lights and hardly have to tap the brakes. This is Texas; it is mostly summer temps here.

Where on earth did you get the idea that 23 is so bad? Out of 4 cars I own only one will get better than 23 on the highway.
1995 Lincoln Town Car gets 15 or 16 city, 24-26 highway.
1995 Mercury Grand Marquis 17 city, 25-27 highway.
Even 1989 Plymouth Voyager 4 cyl got 18/22 new and around 18 overall when last driven.
Our oldies do just about as well or better than the Vibe. We’ve always maintained the old ones well.

Do you have the old ECM? If so, I’d be inclined to just put the old one back in. You don’t want that light on all the time as it will mask actual problems which might need immediate att’n for safety.
We carefully removed the old ecm, using antistatic mats. We can put it back if we need to.
We have an OBD-II reader so we can check periodically for codes should we notice anything different.

Guess 30 overall is just lies. But that’s what we thought we would get. Wonder if a Prius can actually get 50 or high 40’s?


#10

When it comes to the automobile world there are a lot of claims made. Some are true and some are not so true.

Engine characteristics concerning torque, power bands, and so on play a big part in fuel mileage and will have a lot to do with a larger engine in a heavier car getting better fuel mileage when compared to a smaller, perkier engine in a lighter vehicle.

My daughter’s V-6 Mustang gets about 25 on the road for example as did the prior 4 cylinder Mitsubishi Galant she owned. My Lincoln with the 4.6 DOHC will easily tick off 27-28 and at times will hit near 30 for comparison. It’s how the grunt is applied so to speak.

Regarding the Prius. a few years back the BBC show Top Gear ran a Prius on their track while tailing a 400 horsepower BMW in spirited driving. The Prius got about 2 MPG less than the BMW.
As one of their guests on the show stated and who owns 2 of them said in so many words; they will do well if driven in a docile manner.


#11

If your location requires an emissions test, it will fail until you program the ECM with the VIN…Is yours powered by the 1.8L or 2.4L engine?


#12

From the five years my mother has owned her 2010 Prius (purchased July30th 2009) hers has averaged 50mpg in mixed driving with a high of 60mpg on long freeway trips with a little stop&go or 55mpg on a straight highway cruise. 45-50mpg in the winter.

The tires could affect the mileage depending on which Pirelli tires this has they make low rolling resistance tires but also performance tires which would perform better at a possible cost of mileage.

I know on other makes the VIN is programmed into the ECM as another way to prove the ID of the car. But that alone shouldn’t change the mileage one way or another.


#13

I drive a 2006 Town Car. Best I can do on highway driving is 22, and that’s in cool temps without the A/C (not that A/C will make much of a difference). 15 around town. 1997 Grand Marquis and 1993 Crown Vic were about the same. I can’t possibly imagine getting 27 in a Panther car. 2002 Mercury Sable 3.0 DOHC will hit 30 on the highway. The Astro and Silverado we won’t even talk about.

I’m not trying to argue, just saying what my experience is.

A Prius can get in the high 40’s easily if driven in a manner that maximizes regenerative braking, like lots of stop and go and city traffic. Highway mileage is generally worse than city or mixed.


#14

It could be that the Lincoln Marks do a bit better on fuel mileage because of the DOHC engine as they breathe a bit better on the upper end.
Both my current and past Marks have been verified countless times as to fuel mileage and 27 or so on the road is common with those cars unless they’re suffering a bit.

Both of my Marks will tick off 19 MPG in city driving if driven gently and right now with my current mix of about 85% open road/15% city I’m getting right at 25.7. Not too shabby for a fairly heavy RWD V-8 car at all.


#15

"We were told we’d get 29 city and 34 highway on this automatic when we bought it."
And you believed the salesman despite the official EPA ratings? Allow me to suggest that you consider this an education in car buying… NEVER believe a car salesman. Never ever. Even if you want to. ESPECIALLY if you want to.

You had the real information and chose to believe the salesman instead. Now you’re trying to make the car meet the salesman’s exaggerated sales pitch. Don’t. You’ll break a perfectly good car if you persist.

Re: your comment about inflating the tires to the maximum… I too hope you meant the maximum recommended pressure on the door jam FOR YOUR CAR rather than the maximum inflation rating on the tire sidewall. The latter could be dangerous.


#16

I owned a 2005 Pontiac Vibe several years ago. I would have been tickled to death to get 23 mpg in town. The best I ever managed was about 25 mpg on the interstate at 70 mph. Never listen to vehicle sales people. They are in the business of selling…not automotive knowledge.


#17

For whatever reason the Toyota Matrix version of this vehicle has a slightly higher mileage rating…More than anything, driving habits and skill determine fuel mileage…


#18

I agree–as I usually do–with Caddyman regarding personal driving habits as being the most important factor in getting good gas mileage, but I want to point out another possible factor, namely the tires.

The OP states that the car is shod with Pirelli tires. While Pirelli is a good brand, I hope the OP is aware that some of that brand’s tire models feature Low Rolling Resistance (LRR), and others do not. For instance, if he is using Pirelli P Zero tires, they could actually be reducing his gas mileage by 1 mpg or possibly even a bit more.

Are these Pirellis a LRR model?

In any event, the “horrible” gas mileage to which the OP alluded is actually in the normal range for this car and is nothing to be overly concerned about.


#19

“We put in the new filter since we also saw owners claim better mileage and performance.”

The power of wishful thinking. If a different air filter could improve mileage and performance for a few dollars, don’t you think the auto maker would have done so? The performance benefits of a K&N filter for a passenger vehicle are totally imaginary, but of course the manufacturer claims otherwise and the people who have bought one want to believe in the imaginary benefit. Sorry to burst your bubble.


#20

Go 55mph on the interstate for 300 miles and I guarantee you will see over 30mpg in the vibe.