Poor MPG in 2006 Pontiac Vibe--ECM at fault?

I bought a used 2006 Vibe base from a GM dealer a few months ago. Around 95,000 miles now and seems to run good. However, gas mileage is poor, less-than-expected 23 mpg, no matter city or highway, no matter gentle or more aggressive driving.

We replaced air filter, put Techron fuel additive in two times, cleaned MAF sensor, using the excellent instructions we found on this forum. Bought new spark plugs and PCV valve but haven’t put them in yet. Plenty of power and no CEL, so we don’t think O2 sensors or catalytic converter would be the cause.

I searched for reasons for the poor mpg and found a thread about “jack rabbit starts and poor mpg of 19-21” and think mine may have an ECM computer problem. The Vibe was squealing the front tires when we would drive off from a stop. Since they were more worn than the back, I imagine the previous owner had had the same problem for some time. We had the tires rotated so the better ones are on the front.

I looked at the ECM recall threads. Ours is a 89661-02K41. Hard to read those small numbers, but with a mirror, I think mine is 8746, so the chart said it was “good” and not eligible for the replacement under the recall.

I still think the lousy mpg is due to some defect in the computer. Is there any way I can hack the existing computer to fix it to get better mpg? I’ve looked online for used and new replacement ECMs. I’m wary of a used one (from eBay) unless I could get one from an owner who swears he got at least 30 mpg. I’ve also read that swap outs may need programming. Does a dealer have to do it, or can I do it myself? My husband thought of RockAuto as a place that might carry new ECMs. Not sure which ACDelco model to pick there—Vibe is AT, FWD, base w ABS. ACDELCO Part # 19205364 MODULE,Powertrain Control w/ACTIVE BRAKE CONTROL(JL4) or 4-SPD AUTO TRANS(MU4); Base Model. If we have ABS, do we need w/Active brake control? There’s only one choice for the Matrix there: STANDARD MOTOR PRODUCTS Part # EM11375 Reman, which oddly enough is my exact same 89661-02K41, says w/o Traction control.
Can someone advise me on what to do? Has anyone replaced ECM like mine that was not covered in the recall? And where do I complain; maybe there should be an extended recall to cover mine, too.

We like our Vibe, but we would like to get better gas mileage. Thanks.

Try replacing the thermostat.
It’s not expensive and at this age it’s ready to be changed anyway.

@Crispy any PCM for your car must be programmed

You can NOT do that yourself without a pass-thru programming device and a subscription to TIS

You say “The Vibe was squealing the front tires when we would drive off from a stop.” Silly question, but have you tried accelerating more gently? Also, you normally want the better tires on the back. In dry weather it probably won’t matter, but in rain or snow, having significantly worse tires on the back will make the car more likely to spin if you lose traction.

I think it’s extremely unlikely that the ECM is your problem. I would have someone good with driveability problems look at how responsive the O2 sensors are and the fuel trim data. I don’t know what engine you have in your Vibe, but if you’re getting over 20 MPG with a V6 in city driving, that’s not too bad really.

Vibe only comes with 4 cylinder.
One engine version revs higher than the other (Vibe GT),
but both automatics normally average MPG city/highway in the mid to upper 20’s.

Do any of you four who have replied own a Vibe?

Yes, mine is a 4-cylinder 1.8 L. Should be getting 29/34 mpg like most of the other 2006 Vibe owners get.

I’ve always driven like I have an eggshell under my foot; I do not hotrod my car, never have.
No CEL, no smoke, no gasoline smell. Quiet engine, no stall or hesitation.

@db4690-Please explain more about " pass-thru programming device and a subscription to TIS"
Is that Toyota Information Services? Can only a Toyota or GM Pontiac dealer do the programming, or can independent shops do it? Can someone reprogram mine or check it to see if it is working properly?

And, there may be something else we have not thought of, so I am hoping someone out there has some other ideas about why the mpg is so low.


The 2006 Vibe Only has an EPA rating of 23 city so I don’t believe people who claim high 20s in the city. As far as squealing the front tires, I have noyiced over the years that GM provides very agressive throttle linkage that gives you most of the throttle in the first third of the throttle to make their cars seem peppier than they actualy are. You may need an even lighter foot than usual on this car. Make sure your tire pressures are up and check for a dragging brake.

I have a 2006 base Vibe with 102,000 miles. I get 28-30 mpg on my daily commute - about 20 miles each way, mixed city and highway driving. On highway trips, I’ll get 33-35, depending on how I feel that day :wink:

and no squealing of the front tires

Also - I’ve never gotten less than 26 on a tankful. If I were driving in Atlanta or Chicago, I might get less, but in my suburban/small city driving, that’s what I get.

I have a 2006 Matrix 5-speed stickshift.
City MPG 25-28 (winter-summer).
Highway MPG 32-37.
Automatic trans city MPG will be a couple less.
The original tires had lousy grip and could be chirped in 1st or 2nd gear.


Yes, TIS is the toyota information system.

An independent shop could update the PCM . . . if they have the equipment. They will have to have a valid subscription to TIS. Then they download the updated software from TIS and use the passthru device to update your PCM.

This link will explain it better than I just did


If you had an ECU/ECM problem chances are you’d get a check engine light. An ECU either works or it doesn’t.