Odometer rolled back…
Race Director
Joined: Mar 2001
Posts: 19,948
Likes: 6,753
From: Bonneville Salt Flats
Who actually supplied the "VIN check?" What data, from where? Errors are not that uncommon, for both VIN and the info supplied. It's probably more ham-fisted data-entry and/or computer screw-up than anything actually car related. 
Thread Starter
Instructor
Joined: Feb 2024
Posts: 159
Likes: 2
Between myself and the company the car was purchased from there were 3 carfax reports and an other one that I cannot remember the name of.
Just realized that they might be trying a bait and switch. Going to run another one with the company that they used. Just to make sure.
Drifting
Joined: Apr 2018
Posts: 1,609
Likes: 101
From: Camarillo CA
St. Jude Donor '24
Given how hard it is to correct bad data in Carfax, it should be made a lot harder to get careless data into Carfax. Carfax blindly accepting oil change jockey adding a zero is ridiculous.
Drifting
Joined: Aug 2022
Posts: 1,542
Likes: 1,662
From: Cincinnati, OH
I was concerned about this with my purchase too a 2017 with 7500 miles. I was able to check the car fax and see that the mileage was traceable. That was reinforced when I put it on the lift and could see that it appeared to be brand new on the bottom.
Unfortunately there are devices you can get on Ebay, etc., that can alter the odometer reading. I think there are a couple of other areas in the controller where the mileage is stored that can't be erased so if it has been modified you can still get the actual mileage.
Unfortunately there are devices you can get on Ebay, etc., that can alter the odometer reading. I think there are a couple of other areas in the controller where the mileage is stored that can't be erased so if it has been modified you can still get the actual mileage.
Cruiser
Joined: Sep 2021
Posts: 496
Likes: 606
From: NE Ohio
2025 C7 of the Year Finalist - Modified
2024 C7 of the Year Finalist - Modified
Team Owner
Joined: Sep 2010
Posts: 32,042
Likes: 4,610
I recently brought my C7 into the local car super store for a price estimate.
The vin check they did showed a mileage discrepancy and the car being in
two other states(Florida and New Jersey).
I had previously ran two check and the dealer it was bought from and there own check.
Florida and New Jersey did not show on either of those and the loss of mileage.
Messaged the place I bought it from. They are confused about the report. Will see more on Monday what they have to say.
Thinking I’m kinda hosed at this point in time.
Bit long. Thanks for reading.
The vin check they did showed a mileage discrepancy and the car being in
two other states(Florida and New Jersey).
I had previously ran two check and the dealer it was bought from and there own check.
Florida and New Jersey did not show on either of those and the loss of mileage.
Messaged the place I bought it from. They are confused about the report. Will see more on Monday what they have to say.
Thinking I’m kinda hosed at this point in time.
Bit long. Thanks for reading.
Did you get a printout from the dealer you bought it from?
I'd stop by a Chevrolet dealer and see if you can get the GMVIS report of the car. and a Carfax.
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Drifting
Joined: Aug 2022
Posts: 1,542
Likes: 1,662
From: Cincinnati, OH
I have never used one to verify, but they just might work.
https://www.googleadservices.com/pag...BAgCEA8&adurl=
I hope this is correct.
https://www.googleadservices.com/pag...BAgCEA8&adurl=
I hope this is correct.
The milage is stored in the Ometer & body control module They have to
match or the car will not start
match or the car will not start
Last edited by frankbicknell; Jul 9, 2024 at 09:58 AM.
Drifting
Joined: Mar 2022
Posts: 1,388
Likes: 795
From: Indiana
Our odometers can most certainly be rolled back. First legit case to alter the odometer reading is with an instrument panel replacement. Panel explodes, need a replacement, new panel, by law, must be replaced showing last known mileage display of the replaced panel. I believe maybe dealers are the only ones who are supposed to have this ability.
I know they are not, but the person I know with this ability isn't about to go to jail to increase the value of any ones car. It's an electronic device, our cars. Just a different way to pick a lock.
IF this were the case, a knowledgeable tech would be able to see this. I don't think its hard to find.
I know they are not, but the person I know with this ability isn't about to go to jail to increase the value of any ones car. It's an electronic device, our cars. Just a different way to pick a lock.
IF this were the case, a knowledgeable tech would be able to see this. I don't think its hard to find.
Race Director
Joined: Oct 2004
Posts: 13,587
Likes: 1,352
From: Home of the VOLS ! Knoxville, TN. Tennessee
St. Jude Donor '11-'12-'13, '15, '16-'17-'18-'19
Not sure about C7s, but back in my C5 days, I wanted to add HUD to my car once and the cluster did not have that capability.
The seller that sent me the cluster and the projector kit asked for the mileage on my current cluster, and the replacement cluster that was sent out had the stated mileage on it when I installed it.
The seller was not a GM dealer. It was just some dude in SC that did this as a side Hussle.
The seller that sent me the cluster and the projector kit asked for the mileage on my current cluster, and the replacement cluster that was sent out had the stated mileage on it when I installed it.
The seller was not a GM dealer. It was just some dude in SC that did this as a side Hussle.
Drifting
Joined: Aug 2022
Posts: 1,542
Likes: 1,662
From: Cincinnati, OH
In addition to the other things I mentioned above, the big thing I forgot to include, that made me feel confident in the odometer reading in my car, is that I purchased from a very reputable chevy dealer.
Le Mans Master
Joined: Oct 2005
Posts: 7,002
Likes: 2,679
Odometer is usually stored in 2-3 modules (PCM/ECM for sure but also BCM or even ABS). Yes it can be modified, but it's not easy (the tools to do it perform a man in the middle attack to trick the modules who are talking to each other that the value is different).
But with these being so close that is unlikely, most odometer fraud involves warranties. Because people who put on mondo mileage in 3-5 years want to use the B2B and the Powertrain Warranty.
If your car is over 5 years old the only reason to modify the odometer is to take it back under 100k (there is a "significant" loss in value when a car crests 100k, it's a mental thing on the buyer side).
EDIT: Usually odometer isn't stored in the cluster, because those can be replaced rather easily. I can't remember GM's specifics but another module it can be in is some sort of gateway as well. Regardless its always in 2 modules. Never only in one unless you go to older pre-CAN based cars.
But with these being so close that is unlikely, most odometer fraud involves warranties. Because people who put on mondo mileage in 3-5 years want to use the B2B and the Powertrain Warranty.
If your car is over 5 years old the only reason to modify the odometer is to take it back under 100k (there is a "significant" loss in value when a car crests 100k, it's a mental thing on the buyer side).
EDIT: Usually odometer isn't stored in the cluster, because those can be replaced rather easily. I can't remember GM's specifics but another module it can be in is some sort of gateway as well. Regardless its always in 2 modules. Never only in one unless you go to older pre-CAN based cars.
Le Mans Master
Joined: Oct 2005
Posts: 7,002
Likes: 2,679
So the service manual doesn't say, can't say I'm shocked, because odometer operation is pretty closely guarded. But some facts. Your mileage can only be calculated by something which knows the car is moving. Only two modules know the movement of the car: ABS and the ECM/PCM/TCM. This is because your speed information is from either Wheel Speed sensors (most common) coming from ABS or a sensor on the output of the transmission (and this sensor can go to the TCM or ECM/PCM, FYI PCM usually is ECM+TCM in one box). So one of these two is the Odometer Master. After that the Odometer is shared with another module who becomes the checker module, sometimes its via a separate calculation (ABS can put the wheel speed sensor values on the CAN Bus, PCM can put the TOS on the CAN Bus too). Your cluster typically just reads whats on the CAN Bus and its not doing any storing or calculation on its own.
In the old days some sort of signal usually from a TOS went directly to the cluster. Once ABS became standard, and we all have wheel speed sensors, most OEMs eliminated the TOS cause it wasn't needed.
In the old days some sort of signal usually from a TOS went directly to the cluster. Once ABS became standard, and we all have wheel speed sensors, most OEMs eliminated the TOS cause it wasn't needed.
Le Mans Master
Joined: Feb 2006
Posts: 5,979
Likes: 4,142
From: Kansas City, MO
So the service manual doesn't say, can't say I'm shocked, because odometer operation is pretty closely guarded. But some facts. Your mileage can only be calculated by something which knows the car is moving. Only two modules know the movement of the car: ABS and the ECM/PCM/TCM. This is because your speed information is from either Wheel Speed sensors (most common) coming from ABS or a sensor on the output of the transmission (and this sensor can go to the TCM or ECM/PCM, FYI PCM usually is ECM+TCM in one box). So one of these two is the Odometer Master. After that the Odometer is shared with another module who becomes the checker module, sometimes its via a separate calculation (ABS can put the wheel speed sensor values on the CAN Bus, PCM can put the TOS on the CAN Bus too). Your cluster typically just reads whats on the CAN Bus and its not doing any storing or calculation on its own.
In the old days some sort of signal usually from a TOS went directly to the cluster. Once ABS became standard, and we all have wheel speed sensors, most OEMs eliminated the TOS cause it wasn't needed.
In the old days some sort of signal usually from a TOS went directly to the cluster. Once ABS became standard, and we all have wheel speed sensors, most OEMs eliminated the TOS cause it wasn't needed.
If people knew how pathetically easy it is to re-write these values on a Global A car, they'd be rightly pissed at GM. You don't even have to pull the modules to do hardware EEPROM re-writes. It can be done with DID writes via the diagnostic protocols.
Oh, and **** Carfax and their poorly sourced, poorly explained, impossible to arbitrate data.
Racer
Joined: Mar 2016
Posts: 441
Likes: 157
From: Sayre PA
Carfax and Autocheck will make corrections quickly if the person or business who made the mistake tells them in writing that the entry was in error. That’s all it takes we do it regularly.
They will not make a correction based on the vehicle owner or anyone else claiming the error is obvious.
They will not make a correction based on the vehicle owner or anyone else claiming the error is obvious.
Le Mans Master
Joined: Oct 2005
Posts: 7,002
Likes: 2,679
It's stored in EEPROM in the IPC, BCM and PCM. IPC and BCM are the only ones involved in displaying it on the dash. PCM copy seems to be more for archival purposes or for estimating the age of the engine or something.
If people knew how pathetically easy it is to re-write these values on a Global A car, they'd be rightly pissed at GM. You don't even have to pull the modules to do hardware EEPROM re-writes. It can be done with DID writes via the diagnostic protocols.
Oh, and **** Carfax and their poorly sourced, poorly explained, impossible to arbitrate data.
If people knew how pathetically easy it is to re-write these values on a Global A car, they'd be rightly pissed at GM. You don't even have to pull the modules to do hardware EEPROM re-writes. It can be done with DID writes via the diagnostic protocols.
Oh, and **** Carfax and their poorly sourced, poorly explained, impossible to arbitrate data.
Still guessing one of those modules makes the value from ABS, unless GM still uses PCM as a storage spot because it actually calculates it (and then send it over CAN to the others). Its gotta be someone who is aware of vehicle speed (which can obviously with time be used to calculate distance) or wheel speeds (usually in rad/s which can be converted to distance covered with tire circumference and time).
Drifting
Joined: Nov 2017
Posts: 1,325
Likes: 581
From: Conway South Carolina
I'm old enough to remember when all you had to do was disconnect the speedometer cable, attach it to a drill, turn it on so it stays running, and let it run for a couple of days. After the odometer rolled 100,000 it would reset to 000,000. Then all you had to do was decide how many miles you wanted to show before you sold the car.
Drifting
Joined: Aug 2022
Posts: 1,542
Likes: 1,662
From: Cincinnati, OH
I'm old enough to remember when all you had to do was disconnect the speedometer cable, attach it to a drill, turn it on so it stays running, and let it run for a couple of days. After the odometer rolled 100,000 it would reset to 000,000. Then all you had to do was decide how many miles you wanted to show before you sold the car.