Mileage not tracking correctly

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Jun 16, 2021 | 08:00 AM

AnotherDeadCylinder

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Mileage not tracking correctly

I have a ‘02 Trans Am and just realized that the mileage is not tracking correctly. It’s reading less mileage than I’m traveling. How do I correct this?

Jun 16, 2021 | 08:20 AM

WhiteBird00

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Are the tires/wheels a different size from stock?

Jun 16, 2021 | 08:25 AM

AnotherDeadCylinder

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Quote:

Originally Posted by WhiteBird00

Are the tires/wheels a different size from stock?

The wheels and tires are both stock, but I’m not the original owner of the car, so I’m not sure what was on there before. Is it something that needs to be changed in the PCM?

Jun 16, 2021 | 02:26 PM

RPM WS6

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From: Schiller Park, ILL Member: #317

If tire diameter hasn't changed, then it seems that the gears must've been swapped (or swapped back to be sold, without proper re-tune) to cause an issue such as this. If so, you would need to re-tune the PCM for the correct (current) final drive ratio, but you'd first have to determine what that ratio is (and there are a couple ways to do this, not sure if you're familiar with such or not).

Jun 16, 2021 | 06:00 PM

wannafbody

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Quote:

Originally Posted by AnotherDeadCylinder

I have a ‘02 Trans Am and just realized that the mileage is not tracking correctly. It’s reading less mileage than I’m traveling. How do I correct this?

Lower mileage being recorded is good in my book. The issue is that the rpm gauge might be off and that could cause an issue in an automatic transmission.

Jun 16, 2021 | 06:06 PM

AnotherDeadCylinder

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Quote:

Originally Posted by RPM WS6

Gear Ratio is stock too, but this answers my question. I wanted to find out if it was something I could fix on my own or if I would have to take it somewhere to have the PCM tuned. Thanks for your help.

Jun 16, 2021 | 09:32 PM

RPM WS6

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From: Schiller Park, ILL Member: #317

Quote:

Originally Posted by AnotherDeadCylinder

It shouldn't need any sort of tuning if the tires and gears are stock, unless they had been previously changed, tuned for, and then returned to stock (to sell, for example) without being re-tuned to stock settings. I can't think of any other possible explanation where tuning would be the answer for a problem like this.