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Hi All
New member – first post; please bear with me as I ramble. I am curious whether pulling the ECM logs (engine control module/unit – the main computer brain) from a C7 Corvette reveals anything about how the car has been treated. I am shopping for a used 2014-2016 manual Z51, but I will be buying it sight unseen, out-of-state since there are no available cars in the color that I want within 200 miles of me. So as part of the checking out process I was going to ask the dealer to send me the ECM logs. Is pulling the logs fairly trivial for the service people? What data are in those logs and how long are they kept in the ECM memory? Thanks everybody – it will be my first Vette ever :tears_of_joy:
 

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Hi All
New member – first post; please bear with me as I ramble. I am curious whether pulling the ECM logs (engine control module/unit – the main computer brain) from a C7 Corvette reveals anything about how the car has been treated. I am shopping for a used 2014-2016 manual Z51, but I will be buying it sight unseen, out-of-state since there are no available cars in the color that I want within 200 miles of me. So as part of the checking out process I was going to ask the dealer to send me the ECM logs. Is pulling the logs fairly trivial for the service people? What data are in those logs and how long are they kept in the ECM memory? Thanks everybody – it will be my first Vette ever :tears_of_joy:
How come no response or info on this?
 

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It's like Area 51. Everybody knows it's there, but nobody wants to admit it.
 
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There is certainly different information from different manufacturers but one thing that is in all the ECM logs have is , in 1000 RPM increments, how much time is spent at that increment. So from 0 to 1000 1000 to 2000 etc. etc. so you can tell whether an engine has been just idling traffic it's whole life and never got up to 3000 RPM ,or if all it's time at 6500 RPM mean the guy beat it… In addition to Alarms ,and how many times overrev, etc. etc.

Here is a sample printout from my merc verado website on a new engine:
 

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Welcome PeterZ51! Glad that "glen e" was able to provide the information you requested. And your questions were really cogent ones.

The ECU also can provide information on how many times its was reflashed (whether because of any GM authorized updates which were performed on it, and/or whether there were any aftermarket tunes). It will also register the maximum power output that the motor has generated -- again giving GM information on potential aftermarket upgrades/tunes.
 

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Welcome to our forum PeterZ51 and best of luck on getting the C7 you want! Please keep us informed as to whether the dealer(s) are willing to supply you the ECM log data.
 

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I would approach the dealer with the concern that you want to be sure that the vehicle was not tuned or "flashed" by a previous owner which would create warranty problems down the road. It is a legitimate concern that the dealer should honor and if they seem reluctant to do so then either ask them to provide a signed statement certifying that the dealer will stand behind any warranty issues that are rejected by the GM mothership due to a previous tune (something the dealer cannot realistically agree to do) or let them know you are walking away. Either of these last two should motivate a good dealer to provide the desired info or if not you should actually walk away from the purchase. More than one customer has found out too late after purchasing a used vehicle that it was tuned by a previous owner and by the time this becomes apparent via a rejected warranty claim months or years later the new owner is out of luck and on the hook for an expensive repair.
 

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While we can opine about what would be nice and or appropriate to gain from ECM logs, I would be highly interested in what any of our supporting dealers can tell us factually is possible. That is, can a dealer actually supply a pending buyer of a used C7 any/all information off of a specific car's ECM log, and if so, would it be intelligible to the 'average joe' without a interpretation guide?
 
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Jeff,

I would also be interested in seeing how much information is available from the current generation ECM/PCM used by GM. The last time I saw one was 5 years ago when I was at a dealer for a recall and the diesel tech showed me the snapshot he had taken from another GMC 2500HD using his standard Tech II and I recall the two things he pointed out to me were the peak torque value and a calibration counter. I was glad it wasn't my Duramax it came from because the hole in that engine's piston wasn't going to be a warranty repair. I am sure far more information is/was available and every dealership is going to have at least one and generally more Tech II tools available. From what I remember the Tech II display for the ECM was very easy to understand.

Hopefully a dealer tech will chime in soon with some additional info although clearly any dealer tech is going to be careful with how much detail is provided because of the concerns about people trying to tune/flash without getting caught.
 

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Hi Peter and welcome!

Generally speaking, used corvettes are a good used car buy. I say this because of the demographic of the average vette owner and the fact that so many low mileage cars are available. The Z51 is the way to go.

I would second all the advice you have already been given.

Buying a used car sight unseen, I think I would stick with dealers.

You want a low mileage C7 Z51 taken in trade from an older person who is a regular customer of the dealer who serviced the car.

I would want to know if the car was taken in trade or acquired at auction. I would shy away from a C7 auction car. Assuming the car was taken in trade, I'd want to know some basic info on the previous owner, like age, smoker etc. Ask the dealer to state in writing the previous owner did not smoke in the car. Ask for the GM service history that they should have (assuming they are a GM dealer and especially if they serviced the car) which should contain more info then the Carfax.

Talk to the forum dealers. The are the largest Corvette dealers in the world and have the most used vettes. They know their customers, and have a good idea what is coming in on trade and when. They all specialize in out of state transactions. Tell them what you want, and my guess is if they don’t have it, they can find it or at least start keeping an eye out for one. Because of the nature of their business, they can be trusted to provide honest info. If you have a little time, better still.

Mike Furman would be my first call. Mike Furman at Criswell Corvette - National Corvette Specialist

If you buy from an individual, you are assuming more risk, but that doesn't mean you can't get a great car and a good value. Just gather the info suggested here and check out the owner as much as possible. Did he buy new, etc.

Good luck. You are going to love it.
 

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Discussion Starter #15
Thanks all for the good advice. Next week I will use the approach suggested by NSC5 to ask for the ECM logs from a couple of dealers that I am "dealing" with. I'll let you know what happens. Dwward also offered good advice. I can tell you that given my restrictions in what I am looking for (coupe, certified, manual, red or yellow, 2014-2016) there are only 10 vehicles that come up on Cars.com within 500 miles of me (St. Louis). Only one is not an auction car!
 

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Great question. Would love to hear more results from dealers or techs!
 

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Peter,
Manual transmissions are going to be a little harder to find as you have found and demand for used Corvettes will tick up as nicer weather is coming so you will need to be prepared to move quickly when you find a likely candidate.

The GM certified pre-owned warranty program brings up an interesting wrinkle and it would be worth pursuing with the dealer if an ECM log is pulled for cars put into this program. The CPO program, like the regular remaining factory warranty for used vehicles, bounces claims for modified vehicles. Unless I intended to tune or otherwise modify a used vehicle thus making the decision to put the warranty in jeopardy I would be extremely cautious in running down the details of any used vehicle that is often tuned or otherwise modified.

I bought one of the first new Duramax diesel pickups after that engine was introduced and the modern high pressure common rail turbo-diesels were like a magnet attracting tuners because it was pretty simple to make dramatic gains in power, at least for the short term. Various fueling and boost "foolers" quickly became common and it wasn't long before GM sent out instructions to techs showing the difference between the normal and modified "starburst" patterns that appear on the piston faces. I think a lot of the overall manufacturer warranty crackdown on tuning/modification came about because the popularity of this with diesels caught the manufacturers by surprise. I currently have a 2006 GMC with the LBZ version of the diesel and it was the first major power upgrade from the original LB7 version. When GM added 60 HP and 170 lb.ft. of torque they also made major changes to the rotating assembly along with some upgrades to the block, turbo-charger and cooling system along with enhancements to the Allison auto. But a number of owners were adding 150-200 HP to the original LB7 engine with no upgrades to the parts which is possible when you aren't a manufacturer intent upon producing a reliable product that will survive the warranty and beyond. At that point I decided I would never buy a used vehicle that was of a commonly modified type. I did break one personal rule and sold my 2001 GMC to a friend but it is still doing fine with original injectors (a weak point of the first gen Duramax) and has had nothing except normal maintenance with no repairs to the powertrain so that turned out OK.
 

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Make sure you ask for the number of over revs and what the highest RPM's recorded are if you are looking at a manual. All it takes is one or two missed downshifts to put the motor well past the redline mechanically, something that's irrelevant with an automatic since it's impossible to select the wrong gear, it won't let you.
 
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