How does odometer and trip meter retain mileage with no battery.

So when I replace my battery and there’s no juice to power the ecu, how does this effect the odometer, trip mileage meter, and 5000 mile maintenance.

Does the odometer have some back up energy source?

 

Flash memory chips im assuming

 

In a nut shell:

Non-volatile memory.

Non-volatile memory (NVM) is a type of computer memory that has the capability to hold saved data even if the power is turned off. Unlike volatile memory, NVM does not require its memory data to be periodically refreshed. It is commonly used for secondary storage or long-term consistent storage.

Probably EEPROMS

https://en.wikipedia.org/wiki/EEPROM

 

Thanks Jimmy, and I can honestly say I never heard of Non-volatile memory until today.

 

ODO will obiviously not reset

trip will.

 

Well actually you can erase an odometer with some wire and a proper power source and some electronics knowledge.

It is quite easy to erase / reprogram an EEPROM.

https://www.toyotanation.com/threads/diy-odometer-reprogramming.782562/

https://www.youtube.com/watch?v=8wygJwWnFm4&feature=emb_logo

 

Well I can imagine how a glitch could really effect the resale of someone’s vehicle if it put an extra 200 thousand miles on the odometer or erased it completely.

 

Or took off 100K Miles...

Many years ago I know "a guy" that leased a vehicle and it had a clause for annual mileage limit or he would have to pay a huge price per mile. Had the old mechanical odometer. Go in with a set of rubber gloves and a set of jewelers screwdrivers... Boom 40K miles removed in less that 30 minutes.

 

One of my cars lost 20K miles when I swapped the instrument cluster from another car. At the time I want trying to roll back miles, just needed a speedometer with a higher limit.

 

Just put the truck on blocks and run it in reverse to roll back the mileage. duh.

 

This actually works on 2018s and below.

 

the older super duties retain there mileage in the dash cluster instead of the ECM, and the truck doesn’t need the cluster to run. so many hot shotters just remove the cluster and drive thousands of miles cross country and when they go to sell the truck reinstall or find a cluster from a lower mileage truck. So on those type trucks when they have such “low mileage”, there are other things to check such as steering wheel wear, seat wear, drivetrain condition, etc to determine if you’re getting false mileage reported. If a deal seems to good to be true, it probably is.

 

So it's not magic fairy farts? You people have utterly ruined this for me

 

Older mechanical odometers were super easy to “adjust”. I had to rebuild a few for my old Mercedes and Buick Roadmasters. Set the mileage to where it was and not lower than it was supposed to be but it’s easily done

 

I'm not sure how Toyota does it. I know GM stored the mileage in the odo and the ecu as well. With one of my cars, neither was the original. I also drove the car without the cluster for a few days. My caddy on the other hand wouldn't even turn over if the cluster wasn't 100% working.

 

No, it doesn't. I know a guy that tried doing that with a drill on the speedometer cable and he found out that the odometer is clutched and only works in the incremental direction. That was on a 1985 Toyota with a mechanical odometer.

It certainly will not work with an electronic odometer. The wheel sensors know which direction they are turning.

 

I believe they generate a pulsed voltage, which is the same regardless of direction of wheel travel, so going in reverse would still add up mileage. The speedometer does not go negative when you drive in reverse, but I never checked the odometer to see if it tacks on miles as you drive in reverse for a significant distance.

 

Magic

 

some call it magic, I’d call it magnetism. Invented many moons ago.

 

ok, let me clarify: