Does anyone know if there is a way to confirm whether a Viper has a factory tune or not? I have a customer who just purchased one from Florida that has American Racing Headers installed. He would like to get some changes made, but does not want to overwrite an aftermarket tune, if one exists.
If it was tuned with HPTuners, you should be able to read out the file since HPT re-enabled the ability to read out the PCM with their custom OS. If you can't, you'll need to verify that the PCM is the stock one, and not a Mopar/Arrow PCM (you'll have to physically look at it to verify that). If none of those check out, then you likely have the stock PCM with the factory tune.
I could probably also give you some behaviors to look for as well - each will have tell-tale signs that you can look for to verify.
Originally Posted by MeentSS02
That would be phenomenal. I tired reading the tune from it, but got the generic response that a stock file was generated for it.
For some reason, VCM Scanner was a real pain to connect to the PCM. The Beta I couldn't get to connect at all. I've just had this happen once before with a newer GM diesel where the customer had a previous tune that was accidentally overwritten, and that was an absolute nightmare
These PCMs are temperamental - you need to turn the key on and let it sit for about 60 seconds before trying to connect to do anything. Even then, sometimes you have to connect a couple of times (especially with the scanner) before it will finally function properly.
As for what you have, there are 4 options (and I think you've already ruled out one of them):
1. OEM PCM with the stock tune
2. OEM PCM with HPTuners
3. Mopar PCM
4. Mopar PCM w/ Arrow reflash
Since you couldn't read out the PCM, you likely don't have #2 (stock PCM with HPTuners). Since the car has headers, you also likely don't have #1 - most Gen 4 (2008-2010) Vipers running headers with the stock PCM will throw codes. If the car runs fine and doesn't throw codes, they likely did something with the O2 sensors (like anti-foulers).
Most Gen 4 guys went with the Mopar PCM when they added headers. There are some tell-tale signs that you are running this, including a bump in idle RPM from 700 (stock) to 750, and a bump in the rev limiter from 6,400 to 6,500 RPMs. The most noticeable difference will be the behavior on decel - when you let off the gas, you should hear no exhaust burble/popping at all. This was disabled, and is unique to the Mopar PCM.
Some guys with the Mopar PCM had their PCMs reflashed by Arrow Racing - this did a couple things in the performance category, including raising the rev limit to 6,600 RPMs. The most noticeable difference with this configuration is also the behavior on decel, but for a very different reason - when you let off the gas under 2,000 RPMs or so, you should hear some very loud popping on decel. There should also be a very noticeable increase in throttle response - with the stock PCM, pushing the gas pedal for the first half inch or so does little to nothing. This was supposed to have been eliminated with the Arrow reflash, but I've never been able to verify that in person.
Bottom line: have the owner go for a drive, and note the behavior on decel. If it doesn't pop, you likely have the Mopar PCM. If it pops ridiculously loud, you likely have the Mopar PCM with the Arrow reflash. Both PCMs eliminate the skip-shift feature as well, although you could do the same thing by installing a resistor in the wiring harness going into the transmission.
If you have the Mopar PCM (with or without the Arrow reflash) and you choose to overwrite the calibration, you'll be back to a stock calibration, and you'll have to go from there. There's no reversing it once done, so keep that in mind. It wouldn't be too hard to recreate, but it also won't be a carbon copy.
Much obliged for your help, sir!
The vehicle in question runs great but does have a check engine light, which is why the customer contacted me. It seems that scenario #1 may be likely as a result. While attempting to read the code out of the PCM, it must have cleared it, because by the time we got VCM scanner working, there were no reported codes left and the check engine light had turned off.
In the meantime, I advised the customer to drive the vehicle until the light comes back so that we can confirm his code before taking any more steps. I have no doubt I'll be able to easily identify which calibration he is running with your very thorough explanation, thanks again!
Depending on what the DTC was. After so many key cycles or drive cycles it may have cleared itself but you might still be able to see it in history codes. Have you tried scanning it with something other than HPT? I have zero experience with that particular platform.
Well, these PCMs throw codes for the dumbest things - por ejemplo, if you disconnect the battery for a short period of time and reconnect it, you get a code that will last at least a couple of drive cycles.
So the customer recently got back to me. The tune in his viper does NOT pop at all. Furthermore, there is a "Rocket Racing Products" sticker on the PCM itself - he sent me a photo of it.
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