My 2016 had a tune and now it doesn't thanks to P2635

Rosedog · September 6, 2018

My wife's 2016 Silverado LTZ Z71 (SCA APEX) was bought used from the dealer back in November 2017, she has just hit 16k miles on it and we're the second owners. The original owner is a pro NFL football player.

Recently my wifes truck started throwing code P2635 and being under factory warranty we took it in. I get a call today from them and they told me the PCM has been modded/tuned and asked if we did it. We did not. Everything on it, is how we bought it. We were told everything on it was legit. They inform me that they have to take the PCM back to factory to properly diagnose it and that it is not covered. It is a $300 fee just to put it back. Then they told me that if I don't put it back to stock that GM would void/blacklist the powertrain warranty.

I balked at that naturally, we didn't do it! You sold it to us that way. We've bought multiple vehicles from you and sent friends to buy from you. Could it have been the previous pro NFL player? Your sales people were giddy when they sold it to us because it had belonged to a NFL player. "I remember that now" is what I'm told. They got the manager involved and waived the fee and are putting back to stock and then moving forward from there.

It would have been nice to know that it had been tuned before hand but this just seems to be par for the course.

I did come across this:

https://gm.oemdtc.com/3236/dtc-p2635-with-p018b-2014-2015-cadillac-chevrolet-gmc

and this bit from HondaHawkGT:

Anyone else run into this?

adamj2121 · September 6, 2018

If the truck has different size tires from factory the "tune" could have just been a speedometer calibrator. It writes the same way as a tune, but doesn't mess with the factory tuning. I haven't experienced the P2635 code, but I would make sure your speedometer is accurate when you receive the truck back and make sure the dealership corrects it if it is not accurate.

wforrest08 · September 6, 2018

The question is how is the stealership determining that your truck is “tuned”? Did they actually look at the parameters for fuel, air, transmission, ect. or are they just going by the flash counter? (all 014+ trucks have a flash counter in the pcm so every time the pcm is flashed it counts as a hit then they compare the number of hits to the number of times they flashed it ie. updates, recalibrations, ect. if the number of hits isn’t the same they determine that somebody else has been in the pcm hence your tuned) Problem with that is every single SCA truck I’ve ever seen is running a lift kit with rims/tires or lowered with rims/tires all GM wheel/tire combos including from the accessories counter all have the same outside diameter so according to GM no need to change that parameter also I believe most/all SCAs I’ve seen have a CAI and exhaust so odds are IMO all SCA trucks are probably “tuned” before they ever leave SCAs shop. I had a local Chevy stealership do my level kit, wheels/tires, ect. on my 015 and asked them before hand how they compensate for the speedo since they can’t use GMs tech tool to do it. (this particular dealership sells in house lifted/lowered trucks and is why I used them) Short answer is a hand held Hypertech Speedometer Calibrator locked to the vin on the truck. So my truck (at that time now is fully tuned warranty blown) showed a extra hit on the hit counter for this and this alone as the Hypertech only changes the parameter for the speedo after making and tire/gear ratio change. So as stated by Adam above if they change all your parameters back to stock and riding high aka lifted with oversized tires your speedo is going to be off along with all your MPG info and possible poor transmission shifts as well.

Did the ball player have a shop tune it or use a hand held tuner himself? Maybe most not all hand held tuners are locked to the vin (so you can’t just buy one tuner for your and all your buddies trucks) so if you want to use it on your next truck or sell it when trading in your current truck you have to put the stock tune back in the truck to unlock it otherwise it won’t work if you try it on another vehicle. Does a guy making a million plus a year care about reselling it probably not? If he had a shop tune it they probably also gave him a hand held loaded with different tunes? Again only way your probably going to find out is by the hit counter.

If this was my truck my next call before having the dealer do anything would be to SCA and explain the situation to them, no not the secretary or parts guy that answers the phone but a tech, manager, owner, ect. type person and get all the info on your truck from them ie. how it left their facility and what tune if any they did to it and how to determine those parameters are the same. Also if they have ever heard of any of their trucks throwing the code yours has ie. known/common issue they already have a solution for. I have to imagine they keep very detailed records of all the trucks they do. Also what is the warranty on a SCA truck and how does that coincide with GMs warranty as I’m assuming your dealership ain’t a SCA authorized dealer/service center and probably don’t really know what they are dealing with. IMO the only real reason to spend what they want on a new SCA, Callaway, Southern Comfort, Roush, ect. vehicle as opposed to buying a stock one and having a local shop build it is to retain/have a warranty and I believe (that means I don’t know) that the builder picks up the tab for the parts/labor that they “voided” by doing what they did to the vehicle if that makes sense. Even if your truck was sold in late 015 it’s still less than 3 years old so if the factory 3/36k comes into play if the tune is deemed to be SCAs then it shouldn’t be put back onto you. You’ll have to check with SCA as far as what these trucks come with for warranty of course and if it transfers ownership assuming it’s SCA stock (no additional mods to the mods they did) and not GM stock. SCA might also be able to make contact with your dealer on your behalf and steer them in the right direction if needed as far as where to go next and what “tune” will be needed if it does need to be “reset” cause if you are riding high like I’m guessing you are your probably going to be extremely disappointed in the performance of the truck with a stock GM tune in it if I’m right...

Edited September 6, 2018 by wforrest08

Rosedog · September 6, 2018

2 hours ago, adamj2121 said:

If the truck has different size tires from factory the "tune" could have just been a speedometer calibrator. It writes the same way as a tune, but doesn't mess with the factory tuning. I haven't experienced the P2635 code, but I would make sure your speedometer is accurate when you receive the truck back and make sure the dealership corrects it if it is not accurate.

Thanks for the heads up.

Rosedog · September 6, 2018

3 hours ago, wforrest08 said:

...

Well I have a call into SCA and I'm waiting for a call back. No mods have been done us since we've owned it.

Edited September 6, 2018 by Rosedog

Rosedog · September 6, 2018

Just got the call from the dealer that the flash back is not taking. Now they're talking about replacing the computer. SCA probably won't get back to me until tomorrow too.

wforrest08 · September 12, 2018

Any update on this?

Rosedog · September 12, 2018

Funny you should ask. I was just thinking of asking the dealer the same question.

Crobinson16 · September 12, 2018

Just curious, was this sold to you as a certified pre-owned. Reason I'm asking is one of the parameters that the dealership is required to check as a certified pre-owned is programming. They are to verify that all ECM, TCM calibrations are factory. There should be a area in the paperwork relating to this. I'll have to see if I can find the paperwork that shows this. Also even if it wasn't, most dealership's around my area check this before selling a pre-owned vehicle , and they also have paperwork asking the seller or person trading in the vehicle if any modifications including non factory tunning or calibrations are installed. Now that doesn't mean the person is going to tell them , however your signature is required stating as such. I don't know the legal aspect of it though.

When I was looking for my new truck and I finally traded in my 2011 for my 2017 I went through this process. And then the same thing at a different dealership even in a nother state when I traded in my 2017 for my 2018. Also when I was looking for a certified pre-owned Silverado for my father we looked at several trucks at different dealerships within the state and I asked to look at all services records and the certified pre-owned paperwork and everyone of them had a check list of checking for non factory tunes and calibrations. Just some information for you to use as you may.

Rosedog · September 12, 2018

Well I got a call from the dealer while I was eating lunch. They're waiting for a call from GM tech engineers on how to get it flashed back (iircc). They said in about two days. What in the world does that mean? I don't know. I'll be calling them back later when I'm prepared to properly talk to them.

Rosedog · September 13, 2018

So in the end I'm being told now that they can't reflash the PCM to stock so they have to replace it, and they're going to replace the fuel pump due to the code being thrown. Parts are on order, should have the truck back Monday. Being told that the used-car manager and dealership owner are covering everything...Personally don't care who is as I know I was not going to be.

adamj2121 · September 14, 2018

21 hours ago, Rosedog said:

So in the end I'm being told now that they can't reflash the PCM to stock so they have to replace it, and they're going to replace the fuel pump due to the code being thrown. Parts are on order, should have the truck back Monday. Being told that the used-car manager and dealership owner are covering everything...Personally don't care who is as I know I was not going to be.

Sounds like they are working to make it right. It's always nice to see a dealership that treats its customers right after a sale. Let us know how the truck is once you get it back!

TJay74 · September 15, 2018

On 9/12/2018 at 2:39 PM, Crobinson16 said:

Just curious, was this sold to you as a certified pre-owned. Reason I'm asking is one of the parameters that the dealership is required to check as a certified pre-owned is programming. They are to verify that all ECM, TCM calibrations are factory. There should be a area in the paperwork relating to this. I'll have to see if I can find the paperwork that shows this. Also even if it wasn't, most dealership's around my area check this before selling a pre-owned vehicle , and they also have paperwork asking the seller or person trading in the vehicle if any modifications including non factory tunning or calibrations are installed. Now that doesn't mean the person is going to tell them , however your signature is required stating as such. I don't know the legal aspect of it though.

When I was looking for my new truck and I finally traded in my 2011 for my 2017 I went through this process. And then the same thing at a different dealership even in a nother state when I traded in my 2017 for my 2018. Also when I was looking for a certified pre-owned Silverado for my father we looked at several trucks at different dealerships within the state and I asked to look at all services records and the certified pre-owned paperwork and everyone of them had a check list of checking for non factory tunes and calibrations. Just some information for you to use as you may.

There is absolutely no way for the dealership to check and or see if the programming is stock or not. AS said, under a warranty claim and it is up to GM as to why or when the GM TAC line will request this, but the TAC line will ask for a snapshot from the laptop while it is plugged into the computer. At that point if things dont line up then GM will have the tech upload the file into the GM system and the TAC line will check the calibration on their side.

The dealership and or the tech do not have a way to see the actual calibration file and to see if the known factory calibration or the last known updated calibration match the one currently in the ECM/TCM.

When I had my 16 in the dealer a couple of months ago for a bad injector the tech was super nice to me about my truck, he knew it had been tuned as when he did a test drive and got on it after coming around a corner started to accelerate he got into enough my truck downshifted and then barked the tires on the 1-2 shift. He could also tell I had turned off the DOD/AFM system as it would never kick on in his test. He told me then a tune isnt a big issue until something majors happens. Bring the truck in for a bad injector, a failure AFM lifter or something and you are fine. Throw a rod out the side of the block and GM will ask for a snap shot and deny the warranty and blacklist the warranty on the vehicle at that point.

In short, unless the previous owner told the dealer the truck was tuned there is nothing that can be done. My guess is the reason the OP ECM failed ot return back to stock is the customer tune was locked by the tuner, when that happens there is nothing that can be done. You can force flash an ECM that has been tuned and the unte is locked, the ECM has to be replaced. The new ECM comes without an OS even loaded onto it, the dealer plugs the new ECM into the truck and connects to the GM Global site and then uploads and flashes the most current firmware GM has on file for that vehicles VIN at that time.

The ECM isnt that expensive either, like around $200 or so.

Edited September 15, 2018 by TJay74

wforrest08 · September 24, 2018

How did you come out on this? And did you ever hear anything out of SCA?

Rosedog · September 25, 2018

21 hours ago, wforrest08 said:

How did you come out on this? And did you ever hear anything out of SCA?

Got the truck back. They replaced the PCM and fuel pump. Now that its back to "stock" I can tell the difference. It doesn't have that low end umpf that it had before. Almost feels like you're in one gear higher than you should be when in automatic. I really do wish I knew what tune was done to it before but I'll have to wait to be out of warranty before going down that road again.

As for SCA they said they only calibrated the speedo.