[DJC]

I bought my car a few months ago from a dealer who couldn’t provide me with details regarding just what parts were swapped in and where it was dyno tuned…. So, beyond the long tubes and the LT2 that I observed when buying the car, I am trying to figure things out.

The work appears to be high quality with good parts, see photos. The car is a stick shift with long tube headers, LT2 intake (with C-8 Corvette cover minus the Corvette logo pieces) and a throttle body adapter plate interface. Exhaust looks like 3” mandrel-bent out to the stock NPP suitcase muffler. Car came to me with no cats at all and no downstream O2 sensors. I was told that these parts were “tuned out.” Luckily, the factory harnesses were not cut off, but simply zip-tied up and out of the way.

I sourced a pair of “pre OBD-2” bullet cats from Summit and had my local shop weld those in, along with bungs for the rear O2 sensors - which also came from Summit. The car ran fine (very strong actually!) this way for a couple months but now I get a code for P015B “O2 sensor Delayed Response Lean to Rich Bank 1 Sensor 1. I think this corresponds to the cylinder 1 upstream sensor. Three codes actually, all read the same but one each for Generic Stored, Pending and Permanent.

I’ve swapped in new O2 sensors but the codes came back anyway. My sensors are:

GM Genuine Parts 12665162 Heated Oxygen Sensor Downstream
GM Genuine Parts 12655677 Heated Oxygen Sensor Upstream

I’ve been checking for obvious clues of a disconnected vacuum line or exhaust leak and I found neither. I have no performance complaints all - this car sounds and runs really strong - fun to drive. Good idle too. I’ve read now about HPTuners and think that their newest MPV13 offering might be a good way to sleuth out just what is happening to get that code to appear.

I wonder if I can get a factory settings PCM file (as-delivered, bone stock) and compare that to the PCM programming currently on my car. I can also try various values for the O2 sensors with HPTuners so I’ve read. It would be nice to code the downstream back in and get it all to work with my high-flown cats but not throw any codes. Am I on the right track here and if so, what’s a good shop to assist me remotely. Or maybe swap in a bone-stock PCM set up for my VIN and save the tuned PCM on the shelf as I make changes to the new PCM? Thanks!

[easttxss]

The only purpose of the rear O2 sensor is to monitor the cats so I would just forget about those since they have been tuned out and are not throwing codes. I think I can see an exhaust leak between cyl 1 & 3 in you picture. Any leak will throw off the sensors. If you replace those gaskets, go back with the factory GM/Mahle gaskets. Use a length of vacuum line in your ear like a stethoscope to pinpoint any leak between head and header, but it will usually leave a black soot at the area of leak.

Also, this thread from 2019 https://www.camaro6.com/forums/showthread.php?t=559945

[DJC]

Thanks for the info and the post link. I checked the header bolts on driver’s side last night and I may have got some tightening on the bolt between cyl 1 and 3. I’ll check again today when I go out to drive. My exhaust shop was worried about the seal with that clamp when they welded in the cats. They decided it was OK after I drove for a week and let them inspect for any soot or traces of leak and found none. Wouldn’t hurt though to pull the clamp, loosen things up, seal as the 2019 post did, and drive some more.

I ordered an HPTuners MV13 and wideband kit from that company last night also. I’ll delve into the details of reading the existing tune, creating a log, and seeing what the engine wants to reveal. I understand thaqt there’s a library of tunes out there that people can try as baselines - even some that allow all four O2 sensors to report in (now that I have cats in).

[easttxss]

Originally Posted by DJC

Thanks for the info and the post link. I checked the header bolts on driver’s side last night and I may have got some tightening on the bolt between cyl 1 and 3. I’ll check again today when I go out to drive. My exhaust shop was worried about the seal with that clamp when they welded in the cats. They decided it was OK after I drove for a week and let them inspect for any soot or traces of leak and found none. Wouldn’t hurt though to pull the clamp, loosen things up, seal as the 2019 post did, and drive some more.

I ordered an HPTuners MV13 and wideband kit from that company last night also. I’ll delve into the details of reading the existing tune, creating a log, and seeing what the engine wants to reveal. I understand thaqt there’s a library of tunes out there that people can try as baselines - even some that allow all four O2 sensors to report in (now that I have cats in).

The HPTuner's tune repository has been drastically cut back in the last few years due to EPA crackdowns. There are very few tunes in it and they are all stock. They have also had to limit what you are able to do with your car, emissions wise, and no one will really talk about it because they don't want to flag the EPA. I have an old MPVI and am not sure I want to upgrade yet due to these changes. You can still share tunes with other members if you find someone that wants to help.

[DJC]

My MPVI3 is on its way. I’ll see what I can glean just from reading (not yet editing anything) the car. I’m reading posts here and on the HP Tuners forum. A common issue seems to be encountering a “locked” PCM after a professional shop has tuned the car. Makes sense to me as you’d want to keep working with them to make things perfect. In my case, I have no idea who or what shop to ask of for more work. Hopefully I can access my PCM and see what’s what. I notice also that it seems to be in V8 mode always, even when cruising with no load in Touring mode. Not sure if that’s from tuning alone or if they removed the DOD parts from the valve train as well. I guess there’s no easy way to see if they did a cam swap besides opening up the motor and inspecting things? The car idles like stock, no idle roughness at all, smooth as glass.

[easttxss]

Originally Posted by DJC

My MPVI3 is on its way. I’ll see what I can glean just from reading (not yet editing anything) the car. I’m reading posts here and on the HP Tuners forum. A common issue seems to be encountering a “locked” PCM after a professional shop has tuned the car. Makes sense to me as you’d want to keep working with them to make things perfect. In my case, I have no idea who or what shop to ask of for more work. Hopefully I can access my PCM and see what’s what. I notice also that it seems to be in V8 mode always, even when cruising with no load in Touring mode. Not sure if that’s from tuning alone or if they removed the DOD parts from the valve train as well. I guess there’s no easy way to see if they did a cam swap besides opening up the motor and inspecting things? The car idles like stock, no idle roughness at all, smooth as glass.

The manual trans cars don't have DOD enabled from the factory. If you look at the harness coming out from under the intake, you will find it's not plugged into anything. The engines are all the same so you do have the DOD lifters and top plate, but you don't have an engine harness for it or enabled in the computer. You also won't have the AFM valves in the exhaust.
My car was previously tuned by someone else but it wasn't locked. I think the general consensus is that its a pretty dick move to lock the ecm.

[DJC]

Very helpful, thanks! I hope mine is also unlocked. If I end up wanting to restore the car to the factory tune as a baseline, can (should) I buy a second PCM already set up for my VIN to swap in place of this one or just save the existing tune and load in a stock tune? The HP Tuners tune library comes up empty when I load in my car details for their search engine. Are the stock tunes same for a 2020 or even earlier? That would expand my searching. I’ll want to stop the explosive nature of start up, having read that on headers cars it’s not needed to warm up the O2 sensors like on the stock exhaust? I’m wanting to bring my car back into a tune state that includes the use of my cats and rear O2’s if possible. Glad to try and make things more compliant, especially if I ever sold or traded the car.

[easttxss]

No need to get a second ECM, just read what you have and compare it to an earlier stock tune to see what is different, which is pretty easy in HPTuners. You can take the startup flare out of it, that's not a problem. A lot of the aftermarket/high flow cat will still set off the check engine light, so you may just leave that alone as long as it's turned off correctly. I didn't like the way mine was done so I went in and corrected it. There are 32 codes that have to be set to 'do not report' so that you don't get any kind of alert, but I'm not even sure you can mess with it with the new updates. You made it compliant just by putting the cats on it. Call it good and move on.

Looks like you also have an E85 sensor on it too, so if you have access to E85 that's cool. I don't have any out here in East Texas

[DJC]

My HP Tuners package arrived today. Now I’ve got my MVPI3 registered with 4 credits and ready to head out to the car tomorrow. I found a 2018 base tune in the HP Tuners library but nothing newer. I also found (on Camaro6 forum) what is supposed to be a 2019 ECM Only base tune. Was the base tune different from year to year or would either of the 2018 or 2019 serve as a base tune for my car? If not, what does, 2020 - up, 2021 only, 2022? Remember, I don’t plan to write the base tune back, just want to run a comparison in the program to see what was changed over stock. I’ll see about softening the startup flare after I get my P015b code to stop coming up. We do have E85, what piece tipped you off in my photos to be the E85 sensor?

[easttxss]

Dont know if there are any changes between the years, haven’t looked at any but mine.

The fuel line across the back of the intake manifold is not stock, the flex fuel sensor is on the passenger side of that hose.


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[DJC]

I read the car and saved the file so I can review it in detail back inside. I went through getting my 4 credits applied to this car and this device. Didn’t buy a 5th credit to write to the FSCM. Would I need to deal with the fuel system in turning off my SES codes for the O2 sensors? Which, by the way, seem grayed out and won’t let me uncheck the SES box. Also no options pull down when I go in the settings box. Software bug with latest software?

[KingLT1]

You have to take the training course for the latest software version and then HPt will give you a access code that unblocks those "grayed out" features.

You only need to license the FSCM if you want to adjust your NPP exhaust settings and fuel pump voltages.

[easttxss]

For the way you bought it, there are 32 codes that need to be unchecked, you only showed one page and the correct ones are, in fact, unchecked. I would leave it alone.

You also don't want to mess with any 'sensor 1' O2 codes, you need those to do their job.

[DJC]

The only code currently thrown is the P015b code. If I don’t turn it off, then I’ll need to adjust the 02 sensor itself to read correctly? Searches under that don’t seem to return a lot of hits.

I did just get a very nice reply from HP Tuners on my support ticket. They explain that I indeed need to complete a free online course that points out the EPA and CARB ramifications of editing certain grayed out parameters. They link to this well-done you tube video. I appreciate this greatly.