2003-2007 Silverado Write Precise Milage

**smeeprom** · 18th February, 2021, 04:21 AM

I was playing around with the odometer readings on 2003-2007 Silverado/Sierra instrument clusters. I cannot get the mileage to display exactly what I want it to.

It gets within 25 miles or so without an issue, and I know that is close enough for any purpose under the sun, but it bothers me that I can't figure out why it does this.

For examples I have attached a ZIP folder with three BIN files, the first is the original hex dump that I pulled from a 2006 Sierra, to test my calculations I modified the hex to 10 F4 FF FF FF 46 which I thought should display 111,111 mi. Instead, it displayed 111,129. I played around with it until I discovered that 10 F4 46 FF FF FF displays 111,111 like I wanted.

Does anyone know how to calculate which location the minor odometer number needs to be for any given mileage without using trial and error?

It's a very minor issue, it just bugs me that I don't understand it.

Thanks for any input!

**smeeprom** · 19th February, 2021, 12:24 AM

Ok, so maybe my entire way of calculating odometer readings is wrong.

I had been reversing those three hex numbers (46 F4 10) and coming up with exact mileage on every cluster I pulled the dump from, but I was reading an ETsmart CALC file just now and they are multiplying the first two hex numbers by 256?

I will try to just use the calculator tonight and see if it displays the exact reading... I would still like to know how to do it manually, just for fun.

Is that separate digit (46 on my 111,111) just a checksum? I'm even more confused now!

Thanks for reading!

**smeeprom** · 19th February, 2021, 03:07 AM

Well, I told the ETsmart calculator to set the miles to 111,111 and it spit out the exact same hex code that I had came up with that actually displayed 111,129. I didn't bother flashing it to the eeprom since I see no way that it could display differently.

Still bugs me that I can read the odometer from the original hex code down to the tenth of a mile, but can't figure out how to correct it nearer than 25 mi or so.

Not that anyone would ever care, but it's just the idea that I can't figure out what the processor is looking at!

I am giving up on this for now, but I will post later if I ever figure it out. (Just in case there is someone else out there like me!)

**clusters** · 19th February, 2021, 04:35 AM

I have never figured out the "floating" fine correction. Plus or minus a few Km has never been a problem for me, and shouldn't be for anyone else.

If you are that anal about it, read the dash, add 1 or 2 Km then read again, repeat until you decipher it.

**jomberykaso** · 19th February, 2021, 04:48 AM

anal?........................

**smeeprom** · 19th February, 2021, 04:57 AM

"Anal retentive" jomberykaso .... what you call someone who is too particular!

**smeeprom** · 19th February, 2021, 05:04 AM

Clusters, I tried adding small increments... Display didn't change until the "major" odometer hex got bumped up, then it jumped about 40 mi.

I'm not actually that particular!!! The main thing is I was enjoying learning to decipher the hex code and the "floating" number wasn't making sense.

Thanks

**smeeprom** · 19th February, 2021, 05:24 AM

Or did you mean let the cluster itself rack up a couple of KM?

I realize that would be the best way to figure it out... just haven't done that yet.

Thought it might be easier to sponge off of your knowledge!

**jomberykaso** · 19th February, 2021, 05:30 AM

Originally Posted by smeeprom

"Anal retentive" jomberykaso .... what you call someone who is too particular!

Thanks for the explanation, where I live we speak in spanish and my english is not so complete due to lack of practice.

**jomberykaso** · 19th February, 2021, 05:33 AM

I think this algorithm to be exact it should be in kilometers

**smeeprom** · 19th February, 2021, 02:47 PM

Originally Posted by jomberykaso

I think this algorithm to be exact it should be in kilometers

I don't think so. I know a lot of clusters are written in KM but these are in miles. I can reliably read the odometer from the hex code.

**jomberykaso** · 19th February, 2021, 02:51 PM

I already know how this algorithm works but the calculation is not exact

**JandJSpeedShop** · 15th March, 2021, 10:52 PM

10 F4 46 FF FF FF FF FF FF FF FF FF will get you what you want

**smeeprom** · 15th March, 2021, 11:44 PM

Originally Posted by JandJSpeedShop

10 F4 46 FF FF FF FF FF FF FF FF FF will get you what you want

You are correct. I discovered that by trying different locations until it displayed 111,111.

My question is, can you predict how many spaces are between the major odometer code (10 F4) and the the minor odometer code (46) on any given mileage?

For instance, can you tell me what would display EXACTLY 222,222 without trial and error? If so, I would LOVE to know how you calculate that!