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Need help with LSA tune / P0151 code on CTS-V
I have a highly modified LSA on a 2014 CTS-V with a custom tune. Tuner no longer around and the car runs fine but it's time for inspection and I'm getting a P0151 code quite frequently. I've replaced the O2 sensors and done my best and I am fairly sure the sensors are working ok. This code points to a malfunction in the sensors but in my case I suspect the car is running WAY lean for a short period - see below.
I have my tune to post and will get logs shortly. The issue occurs in a pretty specific scenario - it happens when the car is just getting warmed up - not cold, but after 2-3 miles of driving, and only when I lift off the throttle and the car goes to idle in gear (auto trans) in the 30-65mph range (so not slow speeds only). I have a wideband and at least confirmed the car isn't running lean under any sort of power situation - so I'm not scared to drive it like this as it's only briefly lean on coast and then only in short bursts just after warming up, then fine after that.
So this is some kind of coast-down, DFCO, or idle airflow issue of some kind. Unfortunately I understand some of the concepts but have pretty much zero tuning experience. I have HPT to make remote tuning support (like this!) easier, but that's about it. I leave changing anything to the experts (like you guys).
The mods are extensive - Tony Mamo ported TFS 255 heads, LT headers, custom cam (medium duration but ~.600 lift), overdriven blower, lots of cooling mods obv, FIC1000 injectors, 102mm TB, large intake, full custom exhaust, and so on and so on...car does have cats and all pre and post-cat O2 sensors, all connected (plus the wideband).
Would greatly appreciate any advice or recommendations and will do my best to capture a log shortly.