Modifying As-Built Data Guide

[solodogg]

I turned that on once for shits and grins. I remember someone saying once that the MPH output wasn't quite right. Does it match up to what the needle indicates? And can you use cruise control while it's enabled?

oddly enough, you are right about it being off. I hadn't paid much attention to the analog speedometer while having it enabled.

Here's the kicker though...you can enable cruise control while in engineering mode. So, sorry for the terribly blurry pic, but the digital speedometer was reading 52.8MPH, cruise showed it was set at 54MPH, speedometer was showing 55 or very very slightly past (even though the angle of the photo makes it look like it was around 57, it was not).

With that said, now i'm curious if the engineering mode speed ever changes with calibration, and maybe it's possible that changing the as-built value is only calibrating the analog speedometer. Guess i'll have to do some playing this weekend again

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[Wally-Bob]

Version 3.0 of my calculator with GPS truing function: https://docs.google.com/spreadsheets/d/1mWnuQZlDTUGjKjmJje1QJIR8Z2c7Kf8KBZxKnw_8EqU/edit?usp=sharing

Nice Job Spart, thanks for this.

And for you guys outside the USA using km/h, if you enter both the Speedometer and GPS in clicks, you will get the correct calibrated Hex value.

 

[Spart]

oddly enough, you are right about it being off. I hadn't paid much attention to the analog speedometer while having it enabled.

Here's the kicker though...you can enable cruise control while in engineering mode. So, sorry for the terribly blurry pic, but the digital speedometer was reading 52.8MPH, cruise showed it was set at 54MPH, speedometer was showing 55 or very very slightly past (even though the angle of the photo makes it look like it was around 57, it was not).

With that said, now i'm curious if the engineering mode speed ever changes with calibration, and maybe it's possible that changing the as-built value is only calibrating the analog speedometer. Guess i'll have to do some playing this weekend again

Maybe that engineering test mode relies on the wheels sensors for data, whereas the speedo relies on the transmission speed sensor? :shrug:

The analog speedometer is pretty precise if you're careful, which is why I suggested using it and trying to place the needle dead-center on a hash mark.

I honestly think that the cruise control uses whatever internally unrounded MPH you happen to be going at the instant you set the cruise. So if you set it for 75mph, internally that could be anywhere from 74.5mph to 75.4mph. And then it's rounded for display as the cruise setting in MPH.

 

[jody858]

Results from lunch:

Cruise set to 68mph
Analog speedo indicates 70mph
Digital speedo (entered using OK button at engine start) indicates ~67mph
Ulysse Speed Pro (phone app) indicates 68mph

So it seems the cruise control displayed the most accurate number, based on my speedo app on my phone using GPS.

 

[Spart]

Results from lunch:

Cruise set to 68mph
Analog speedo indicates 70mph
Digital speedo (entered using OK button at engine start) indicates ~67mph
Ulysse Speed Pro (phone app) indicates 68mph

So it seems the cruise control displayed the most accurate number, based on my speedo app on my phone using GPS.

Again, I honestly think that the cruise control uses whatever internally unrounded MPH you happen to be going at the instant you set the cruise. So if you set it for 75mph, internally that could be anywhere from 74.5mph to 75.4mph. And then it's rounded for display as the cruise setting in MPH.

Also be aware of parallax error when reading your speedometer. Try to get your head centered over the needle, perpendicular to the gauge.

[ame="[MEDIA=youtube]1_Lakjcu9gM[/MEDIA]"]example[/ame]

 

[TexasRebel]

Also be aware of parallax error when reading your speedometer. Try to get your head centered over the needle, perpendicular to the gauge.

I was quite surprised that these Mustangs didn't go to a digital projection of an analog dial for this very reason...

 

[Spart]

I was quite surprised that these Mustangs didn't go to a digital projection of an analog dial for this very reason...

I just wish we all had a digital speedo in the center information screen like the GT350's.

 

[TexasRebel]

I just wish we all had a digital speedo in the center information screen like the GT350's.

I prefer the needle.

My Harley had a DRO tach that I couldn't stand so I replaced it. Knowing the number is great, but watching the movement of the needle tells you quite a bit!

 

[Spart]

I prefer the needle.

My Harley had a DRO tach that I couldn't stand so I replaced it. Knowing the number is great, but watching the movement of the needle tells you quite a bit!

Well yeah, you get both with the GT350.

My favorite instrument clusters have been on my Mini's and RX8 - a center tach with a digital speedo inside of it.

 

[HoosierDaddy]

Results from lunch:

Cruise set to 68mph
Analog speedo indicates 70mph
Digital speedo (entered using OK button at engine start) indicates ~67mph
Ulysse Speed Pro (phone app) indicates 68mph

So it seems the cruise control displayed the most accurate number, based on my speedo app on my phone using GPS.

The analog will appear slightly different with just a small head movement side to side. Plus, car makers tend to do similar things and my Cadillac re-calibrates zero every time you start it. So it may appear to read a bit high (compared to the digital speedo) one time and a bit low another time. Wouldn't be surprised if its the same in the Mustang.

 

[solodogg]

so i just noticed tonight on the wifes edge that modifying the speedometer calibration results in a P160A code being set in the PCM that cannot be cleared. I went back and verified that I do also get the same code in the mustang after modifying thus value.

This seems to be normal for anyone calibrating the speedometer from reading online, and nobody seems to know how to make it go away. Not sure if this would cause any issues at the dealership or not, but it does not set the CEL nor appear to affect anything negatively other than showing a DCT when scanning.

Just wanted to give a heads up

 

[psoff]

so i just noticed tonight on the wifes edge that modifying the speedometer calibration results in a P160A code being set in the PCM that cannot be cleared. I went back and verified that I do also get the same code in the mustang after modifying thus value.

This seems to be normal for anyone calibrating the speedometer from reading online, and nobody seems to know how to make it go away. Not sure if this would cause any issues at the dealership or not, but it does not set the CEL nor appear to affect anything negatively other than showing a DCT when scanning.

Just wanted to give a heads up

My guess is that is done so that people can not change it to keep the mileage much lower than actual. then try to trade it in or turn in a lease. It will probably be a permanent record that is there for good.

 

[Spart]

My guess is that is done so that people can not change it to keep the mileage much lower than actual. then try to trade it in or turn in a lease. It will probably be a permanent record that is there for good.

Nah, the F150 guys were getting something similar but they said the DCT can be cleared if you set the BCM value back to factory.

I don't think it's anything worth worrying about, seems like it's basically reporting as a warning that the data from the transmission speed sensor is off from the ABS wheel sensors, hence no check engine light (because it's a redundancy check rather than the ABS or ESC going wrong.) From doing some reading, if you would have had the dealer change your tire size to one of the other factory sizes in IDS, you'd get the same DTC and there's nothing they can do. It's a value in the PCM that has to be changed to match the BCM and their equipment apparently isn't capable?

Interestingly the Hypertech speedometer calibrator changes both the BCM and the PCM and you don't get a DTC, but I'd think your PCM flash count might go up by one using that device.

More reading on F150forum.com: http://www.f150forum.com/f31/correct-your-speedometer-error-no-flash-tune-required-361473/

 

[Redraven571]

Nah, the F150 guys were getting something similar but they said the DCT can be cleared if you set the BCM value back to factory.

Confirmed! As I posted previously, I changed mine then went back to factory. I went out a little while ago and pulled the error code, I cleared the DCT and it seems to stay cleared.

 

[SloSVO]

Sorry to add this to the speedo talk.. but was curious if anyone has figured out how to disable the TPMS system?

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