Odometer Power Source

[Green]

I am going to be droping a CAI into my protege soon, and all the tutorials I have read say to disconnect the neg. battery terminal to clear the ECU overnight. Well, I have no problem with that, but then it occurred to me, the odometer is powered. I wondered if disconnecting the battery is going to clear the odometer? that wouldn't be good. But then again, why would the mazda designers make it so that every time someone had to replace their battery, the odo died. I don't think they would.

So, my question is, How is the odometer powered?

[chrisf]

It's most likely a bit of flash memory. In any case, it won't clear regardless of how long it's left unpowered. Just imagine the odometer fraud if it did.

[zerocover]

I think there is a back up battery in there to keep the mileage stored.
Dont worry about it the odo will work fine after word.

[Green]

Yah, I sort of figured that they would need it to stay powered somehow, even in the event of a disconnected battery. I was just sort of curious about how it was powered.

Thanks for the reassurance though.

[chrisf]

No, there is no battery.

[kansei]

there is a micro-computer built in the instrument cluster that will keep the odo alive .