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· Registered
247 Posts
Discussion Starter · #1 ·
Here’s how to reprogram your instrument cluster after replacement.

An instrument cluster needs to be reprogrammed after a cluster swap or replacement.
Disclaimer: Misrepresenting the mileage on a vehicle is illegal. However, reprogramming your own cluster is not illegal.
In this case I’m swapping clusters on a Corolla to one with a tachometer and thermometer. The original mileage is 204K

Mileage on the new cluster is 307K

The simple way is to swap the odometer/speedometer sub assembly. But that won’t work if you are going from miles to kilometers, so you’ll have to open the clusters up to reprogram the chip.

Remove the speedo/odo section:

This is the EEPROM chip that stores the odometer and trip computer information:

Desolder the chip

It’s a 93c46 Microwire EEPROM chip:

I made a little EEPROM reader to connect to the serial port on the PC for a few bucks in resistors and diodes. You can also buy a separate USB EEPROM reader for at least $10.

This is the circuit I used to read/write to the chip:

I used ponyprog to dump the contents of the chip. The odometer information is stored in inverted hex characters, three times in the hex dump:

I made a chart to demonstrate the inverted hex decoding, in my case going from 307K to 204K

Once the new dump is written to the chip, I can resolder the EEPROM back to the circuit board.

To check the odometer reading, I can power the circuit by applying 12V to these two screw points:

And you can see the odometer reading has now been corrected to 204K

Now I can enjoy my new cluster with a tachometer, and not have to worry about a misrepresented odometer!

Note: For those suffering from the 299K pause on Corolla, Matrix and Vibe odometers, this method can be used to reset the mileage (or bump it up past 300K) so you can properly keep track of mileage again.

· Elvira
4,386 Posts
Another great post. Very informative.

Which leads to me to say this.....

If some criminally intent mind requires them to rollback an odometer in this manner, why aren't they using that knowledge for good ?

^^^^^^^^^^^^ that is not directed at you @speedkar9

That's not your brothers Corolla :devil

· Super Moderator
5,219 Posts
Some Russians in FL got prison time for rolling back and selling cars with "low miles". There are some Europeans in MN that fix cars for living and some of them do the same. Very unscrupulous of them.

· Registered
1,945 Posts
Though, I think thought ECU controlled speedo memory. So when a dealer replaces a Honda unit, they kick in the HDS to push the odometer reading to the new unit. ECU it probably checked for every car since 1996 for true odo information, to keep the milage from being read by a hacked speedo unit when verified for service.

Yes this info cannot be assumed that it will not be used for bad intentions. Even under the best intentions. Just by the wording of the post makes one think oh let's roll back my odo before I sell and make extra money from it.

I use to think extracting and saving viruses from infected system and executables were fun as to own them in my library of oddities. Once I found out the laws about knowingly having them stored on disc made me quit and destroyed them.

Since then I don't do much with stuff that can be resold. The few tweaks I do to my tablet would get me into trouble, but nobody can prove it unless they are using the tablet with me.

So with today's tech and laws, just having tools of the trade at home can be incriminating, whether or not you do such work on the job. The laws don't care as they are concerned it's no different than busting up a so called bomb maker, just because he stores gas for his lawn mower and has ammonium nitrate for his public flower and veggie garden. They don't care who you are, just proof by what you have for capabilities. Who knows maybe a crack down force will be at your door for making Kodi boxes. Just because there is so much pressure from the entertainment industry.
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