Chevrolet (03-06) Instrument Cluster EEPROM info
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Rough draft status....
Instrument cluster EEPROM is a SOIC8 AT25020A (GM P/N: 56585 for 03-04)
- Datasheet: File:Atmel AT25020.pdf
| Data | Location | Notes |
|---|---|---|
| Mileage | xnnnn-nnnnh | |
| Hours | 0x0504-0505h | |
| Temp Gauge | 0x000059h | 0 – Yes 1 – No |
Mileage Notes
The mileage is a bit tricky, as it’s encoded in HEX, and it’s written in three places for data integrity. If you bought a used cluster off eBay, or went to the local Pick N Pull, but you have your original cluster still you can just use the SPI programmer to dump the contents of the EEPROM on your original cluster, and then program this into the chip on the new cluster and away you go – this will copy the mileage and the VIN over as well as your trip meter, engine hour meter, and settings from the old cluster. Since I didn’t have access to the old cluster, but I did know what the truck’s correct was I had to program it myself. The mileage is stored down to the tenth of a mile but the odometer doesn’t display the tenth. In my example photo above, the mileage is recorded as 15 EC 3D which converted to decimal is 1,436,733 or 143,673.3 miles. Convert the correct mileage to hexadecimal and write these back to the EEPROM to correct the mileage. For example, if the correct mileage is 150,000 you would convert 1,500,000 to hexadecimal and write this back to the chip. Remember the last two bytes are written sequentially over a range of addresses for wear leveling so the last two are not necessarily going to be next to the first four bytes, and you need to change all three copies.