Odometer vs PCM mileage

[Ramitiner]

OK I have to know the real freaking answer here... Some say the pcm holds the mileage as well as the odometer... Now, I got a question... If the pcm holds the mileage then why is it that the folks with tuned pcms swap them out when they go to the stealership? What mileage is in that new pcm? What's the real story with this?

 

[CuylerTech]

PCM stores the mileage as well as most of the other modules do. If you swap out the original PCM it'll throw a code but wont trigger the CEL saying that the PCM was replaced with a non original one. By swapping the original back in it'll clear the flag. If a dealer cared, they can easily tell if its been swapped out.

 

[Ramitiner]

What other modules hold the mileage then? Thought the pcm was a consolidated module

 

[Ramitiner]

I'm going to word it differently this time...

Let's say your evic cluster goes bad (for whatever reason) and you finally get a new one... How can you get your true mileage from the vehicle to program the new cluster?

Not sure why this is bothering me as much as it is but it is.

Just had my brother in law have to rebuild his engine. He bought a car with 65k miles and when the rebuild was taking place the mechanic said that engine had at least 3Xs that...

 

[Rampant]

This was the response to a similar question from a Ram tech on another forum:

"The Mileage is stored in the Cluster and PCM but they get the mileage signal independently. The PCM mileage is used for emissions test calibrations and maintenance, AND can be adjusted to match cluster mileage by the dealer. Cluster mileage cannot be adjusted by the dealer and has to be sent to a service center or a replacement cluster is sent with the mileage already burned in it. Yes the service center fires up the old one to check if its the same as the new one. Many lease customers are caught tampering with the mileage by checking the PCM mileage and warranty records as soon as the car is hooked up to the diagnostic machine the VIN and mileage are sent to chrysler."

Basically, if you replace a cluster with a used one, it will read whatever was on it from the previous vehicle. If you hook up a scan tool, it will show the actual mileage from the vehicle, stored in the PCM and possibly several other places. Its playing with fire unless properly documented. That's one way they catch people trying to tamper with mileage. The different modules which store the odometer info also changes periodically to make it harder for would-be hackers to cover their tracks.

 

[Ramitiner]

This was the response to a similar question from a Ram tech on another forum:

"The Mileage is stored in the Cluster and PCM but they get the mileage signal independently. The PCM mileage is used for emissions test calibrations and maintenance, AND can be adjusted to match cluster mileage by the dealer. Cluster mileage cannot be adjusted by the dealer and has to be sent to a service center or a replacement cluster is sent with the mileage already burned in it. Yes the service center fires up the old one to check if its the same as the new one. Many lease customers are caught tampering with the mileage by checking the PCM mileage and warranty records as soon as the car is hooked up to the diagnostic machine the VIN and mileage are sent to chrysler."

Basically, if you replace a cluster with a used one, it will read whatever was on it from the previous vehicle. If you hook up a scan tool, it will show the actual mileage from the vehicle, stored in the PCM and possibly several other places. Its playing with fire unless properly documented. That's one way they catch people trying to tamper with mileage. The different modules which store the odometer info also changes periodically to make it harder for would-be hackers to cover their tracks.

Boom! Thank you much! Exactly what I was looking for. This is one of the reasons I'm nervous about getting a tuned pcm... The mileage will never match and they might think I messed with it. These guys better hurry up and break the code for the PCMs so we don't have to switch

 

[Ramitiner]

So just to be clear... I'm my scenario the dealer could get the correct mileage off of the pcm so you could put it into the evic cluster... Right?

 

[Ramitiner]

This was the response to a similar question from a Ram tech on another forum:

"The Mileage is stored in the Cluster and PCM but they get the mileage signal independently. The PCM mileage is used for emissions test calibrations and maintenance, AND can be adjusted to match cluster mileage by the dealer. Cluster mileage cannot be adjusted by the dealer and has to be sent to a service center or a replacement cluster is sent with the mileage already burned in it. Yes the service center fires up the old one to check if its the same as the new one. Many lease customers are caught tampering with the mileage by checking the PCM mileage and warranty records as soon as the car is hooked up to the diagnostic machine the VIN and mileage are sent to chrysler."

Basically, if you replace a cluster with a used one, it will read whatever was on it from the previous vehicle. If you hook up a scan tool, it will show the actual mileage from the vehicle, stored in the PCM and possibly several other places. Its playing with fire unless properly documented. That's one way they catch people trying to tamper with mileage. The different modules which store the odometer info also changes periodically to make it harder for would-be hackers to cover their tracks.

Better yet, what scan tool could read the pcm mileage? How would you know if it's reading it from the cluster of the pan?

 

[Rampant]

Yes, they can get your actual vehicle mileage. To do it legitimately, the old and new clusters should be sent to an independent service center who can reprogram and certify the new cluster. They should issue a decal to be affixed to the vehicle with the certification and pertinent info.

You need an advanced scan tool like a Snap-on Verus or Autel Maxisys, etc., to read the modules. The dealer will use a WiTech. Most garages these days have scan tools capable of getting that info.

 

[Ramitiner]

I swear if I ever buy a used vehicle I want a scanner capable of reading mileage out of the cpu/pcm... Not trusting anyone anymore

 

[Ramitiner]

That witech tool and software really isn't that expensive actually... Wonder if they'll sell a normal person the license

 

[Pull Ya]

When you change PCM's on your truck after tuning it and then change back to the original PCM when going to the dealership, you're just gambling that the dealer will not compare the mileage on the PCM and the mileage on the truck. In my experience the dealer rarely does this unless the warranty claim is substantial or unless the warranty work needs to be approved by the factory. A solution might be, take responsibility for tuning your truck and put some money aside to pay for any damage the tuner might cause.
Jay

 

[Ramitiner]

When you change PCM's on your truck after tuning it and then change back to the original PCM when going to the dealership, you're just gambling that the dealer will not compare the mileage on the PCM and the mileage on the truck. In my experience the dealer rarely does this unless the warranty claim is substantial or unless the warranty work needs to be approved by the factory. A solution might be, take responsibility for tuning your truck and put some money aside to pay for any damage the tuner might cause.
Jay

Theoretically the entire warranty would be void the moment you slap on the tuned pcm... Because the mileage can no longer be truly verified via the pcm then how can the warranty still be good?

 

[Pull Ya]

That's a good question. My gut feeling is that under those circumstances, any warranty decision they make will be in THEIR favor. If you want to fight with them, I assume they have a whole room full of attorneys at their disposal. That's why I recommend you have a stash somewhere to pay for any misdeed the tuner(or operator)may cause.
Jay

 

[Rampant]

From what I've been reading, its not just the PCM and cluster that stores mileage info. They store the info in several different modules. They change where they store it by model and year and hold that info close to the vest. If they didn't, you could probably hack your mileage easily with some $10 Chinese eBay dongle.

In any given year, one of the modules is deemed "THE black box" and stores the info. In turn, it feeds the other modules with the info. You're not going to know which module that is without an advanced scanner, pin numbers, and access to factory info.

 

[Ramitiner]

That makes sense but even harder for the lil guy to find out the true mileage of a used vehicle unfortunately

 

[kukufixer]

Theoretically the entire warranty would be void the moment you slap on the tuned pcm... Because the mileage can no longer be truly verified via the pcm then how can the warranty still be good?

Send your original pcm to be tuned and returned to you. I sent mine to GDE on a Tues morning by USPS Priority Express and had it back Friday.

 

[JPT]

Send your original pcm to be tuned and returned to you. I sent mine to GDE on a Tues morning by USPS Priority Express and had it back Friday.

This will void the extended warranty, and potentially make it a nightmare to get any major regular warranty work.

 

[Ramitiner]

exactly

 

[Jeff-M-B]

A lot of important information from the contributors here. Thanks. I'm interested in this kind of information because I'm concerned that a dealer sold be a 2016 Ram Sport with mileage rollback. Truck had what was shown as 24,500 miles on it yet the tires show like they need replacing, fairly soon. My bad, missed that one. Truck was a lease and all service and inspections were done by this dealer according to Carfax. I asked this dealer for all maintenance and inspection docs twice and still haven't received them. I'm planning on taking the truck to my honest mechanic to see if it was tampered with. Then take it from there.