Speedometer Value Change?

[deputylynch]

I have a 2024 Maverick Lariat that's speedometer is off and I can't get anything to change when using Forscan!

My original circumference was 2238 and I went down to 1900 and up to 2500 and it didn't change anything!

I reboot the IPC, BCM, PCM, and ABS modules every time.

I didn't get any codes which I guess is a good thing but it also doesn't change anything?

When I made the changes, I rescanned and it shows the new value, but again nothing changes on the truck; like I didn't do anything at all.

HELP!!

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[Chops]

How to you test your speedometer accuracy? I know about mileposts on roads meant to check odometer accuracy. Are you using those with a stopwatch to measure your speedometer?

 

[deputylynch]

How to you test your speedometer accuracy? I know about mileposts on roads meant to check odometer accuracy. Are you using those with a stopwatch to measure your speedometer?

From the milepost on most Interstate Highways is how I saw the odometer was off as well as the speedometer compared to numerous GPS units.

 

[Chops]

From the milepost on most Interstate Highways is how I saw the odometer was off as well as the speedometer compared to numerous GPS units.

Interesting. So one can understate their odometer by using larger tires? Might come in handy when selling your truck

 

[deputylynch]

Interesting. So one can understate their odometer by using larger tires? Might come in handy when selling your truck

My problem is it is always saying I'm going further and faster than I actually am.

 

[Chops]

My problem is it is always saying I'm going further and faster than I actually am.

That sucks.

Larger tires than OEM will understate your speed & Odo.

Smaller tires than OEM will overstate them them both - not good.

Are you running smaller tires than OEM
and your computer is not compensating?

 

[Lone Ridr]

Mile markers are not perfectly spaced due to interference like bridges, overpasses, construction etc. They may be placed a few hundred feet off from the true mile. The road worker who planted (installed) the sign may not have given a rat’s behind and felt that somewhere close was good enough. IMO Mile markers are not an accurate tool for speedometer checks but they may be close enough.

When I worked at a dealership many moons ago, I took a measuring wheel to a lightly traveled 4-lane road, Southlane Drive, close to the dealership and measured off 1 mile and spray-painted a vertical black line on the guard rail at the beginning and the end of my measured mile. When a customer complained about the speedometer accuracy, usually initiated by a speeding ticket, I would take the vehicle to Southlane and check the odometer reading coming and going.

This may seem like overkill but measuring wheels are cheap. I still have one in the garage from my mechanical designer days. I calibrated the wheel using a laser at 100 yards over flat terrain. Walking a mile is good exercise if you don’t get run over by an inattentive driver.

Another way we checked speedometers was following the service truck on Southlane. The service truck driver would cruise at 50mph and signal me with 5 fingers extended. He would then go up to 60mph, hold his speed and give me a thumbs up. A friend or significant other can help with this crude test. Hmmmmm, if there is a discrepancy, which speedo is correct???

 

[Tbone289]

GPS units and GPS phone apps can be accurate to within 1 mph at steady-state highway speeds and clear skies. It would certainly be more accurate than a stopwatch or comparing to another speedometer.

 

[Lone Ridr]

Having used GPS to verify design work and find and mark graves, I know they are not accurate with the exception of the FARO system which is dead-nuts accurate for static measurements. GPS readings are subject to user error which could account for my distrust.

 

[Chops]

I have a 2024 Maverick Lariat that's speedometer is off and I can't get anything to change when using Forscan!

My original circumference was 2238 and I went down to 1900 and up to 2500 and it didn't change anything!

I reboot the IPC, BCM, PCM, and ABS modules every time.

I didn't get any codes which I guess is a good thing but it also doesn't change anything?

When I made the changes, I rescanned and it shows the new value, but again nothing changes on the truck; like I didn't do anything at all.

HELP!!

You can enter the “Engineering Mode” in your Maverick settings to recalibrate tire size I believe? Might be more accurate than Forscan?

Not sure how to enter the “Engineering Mode” on my Maverick - but when I put bigger tires on I’ll probably just leave it be.

This will understate my ODO yes. But when I drive at the speed limit I won’t get in the way as much - local drivers here drive 5 mph over the speed limit typically

 

[deputylynch]

You can enter the “Engineering Mode” in your Maverick settings to recalibrate tire size I believe? Might be more accurate than Forscan?

Not sure how to enter the “Engineering Mode” on my Maverick - but when I put bigger tires on I’ll probably just leave it be.

This will understate my ODO yes. But when I drive at the speed limit I won’t get in the way as much - local drivers here drive 5 mph over the speed limit typically

The only way that anybody has stated to recalibrate tire size is through forscan.

 

[deputylynch]

Mile markers are not perfectly spaced due to interference like bridges, overpasses, construction etc. They may be placed a few hundred feet off from the true mile. The road worker who planted (installed) the sign may not have given a rat’s behind and felt that somewhere close was good enough. IMO Mile markers are not an accurate tool for speedometer checks but they may be close enough.

When I worked at a dealership many moons ago, I took a measuring wheel to a lightly traveled 4-lane road, Southlane Drive, close to the dealership and measured off 1 mile and spray-painted a vertical black line on the guard rail at the beginning and the end of my measured mile. When a customer complained about the speedometer accuracy, usually initiated by a speeding ticket, I would take the vehicle to Southlane and check the odometer reading coming and going.

This may seem like overkill but measuring wheels are cheap. I still have one in the garage from my mechanical designer days. I calibrated the wheel using a laser at 100 yards over flat terrain. Walking a mile is good exercise if you don’t get run over by an inattentive driver.

Another way we checked speedometers was following the service truck on Southlane. The service truck driver would cruise at 50mph and signal me with 5 fingers extended. He would then go up to 60mph, hold his speed and give me a thumbs up. A friend or significant other can help with this crude test. Hmmmmm, if there is a discrepancy, which speedo is correct???

I would agree with human error but when tested at numerous times on numerous highways and with various GPS it's consistent in its inaccuracy.

I wouldn't mind if it read low but the odometer and speedometer are reading higher than actual.

 

[Tbone289]

Having used GPS to verify design work and find and mark graves, I know they are not accurate with the exception of the FARO system which is dead-nuts accurate for static measurements. GPS readings are subject to user error which could account for my distrust.

GPS in clear areas has an inaccuracy of up to a couple of feet. The effect of that inaccuracy is of much greater importance to design work and locating graves than measuring speed with clear skies on the highway. I would argue that stopwatches on the highway are at least as inaccurate and subject to user error.

 

[Chops]

The only way that anybody has stated to recalibrate tire size is through forscan.

You are correct - can’t use the “engineering mode” as I suggested. Oh well.

 

[HeyBales]

Engineering Mode is changing the DTE calibration setting.
That's all.
Therefore the avg MPG calculation too.
But not speedometer or tracked mileage.

OP - perhaps posting where you made the changes in Forscan would allow someone to notice you missed something.
Because it sounds like the 3 times it's been done - never saw a change.

https://www.mavericktruckclub.com/forum/threads/forscan-speedometer-tire-size-calibration.53836/

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