This CEL started after my last oil change and the software on the vehicle was updated by the dealer.

My main question: could this be related to the exhaust valve simulators used with aftermarket, non-NPP exhausts on an NPP vehicle?

I plan to bring it to the dealer to inspect given it is under warranty. However, I did not want a bill if it turns out that this is related to the exhaust modifications and not covered under warranty.
I also figured it may have been bad gas, but that does not appear to be the case.

 

These codes are because the computer thinks the car is running too lean. They could be caused by an exhaust leak allowing air to be drawn into the exhaust causing the O2 sensors to report a lean condition.

 

Thanks. I have 12k miles since the exhaust install. I will go through and check what I can before bringing to the dealer. I just wanted to see if the NPP simulators may cause this. I did not think they would, but wanted to check.

 

I haven't heard of the NPP simulators or lack of NPP valves causing this error code. But, in theory, if the AFM valves aren't installed then it could cause some unexpected things to happen in the exhaust during V4 mode. A dealer could try to blame the lack of AFM valves if that is the case.

The codes listed are for the O2 sensors upstream of the catalytic converter so it is unlikely that stuff downstream of the cats is causing this (assuming you have the OEM cats).

 

P0170 indicates fuel trim system lean. And, I think P0174 indicates fuel trim system lean bank 2. And its further described this way in the Service Manual:

"The ECM controls a closed loop air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and
emission control. The ECM monitors the heated oxygen sensor (HO2S) signal voltage and adjusts the fuel delivery based on the signal voltage
while in closed loop. The short term fuel trim values change rapidly in response to the HO2S signal voltages. These changes fine tune the engine
fueling. The long term fuel trim values change in response to trends in the short term fuel trim. The long term fuel trim makes coarse adjustments to
fueling in order to re-center and restore control to short term fuel trim. The ideal fuel trim values are around 0. A positive fuel trim value
indicates that the ECM is adding fuel in order to compensate for a lean condition. A negative fuel trim value indicates that the ECM is reducing the
amount of fuel in order to compensate for a rich condition."

There is along list of conditions for setting the DTC - but its set when
"Long Term Fuel Trim = Not within a calibrated range"

It does not seem like simulators could cause this. But aftermarket exhaust system components might. The only thing the car knows is that the fuel trim is out of the expected range - diagnostics are required to determine why that is happening. The service manual actually says this about the possible causes due to aftermarket components:

"Aftermarket equipment/accessories that may cause a DTC to set:
Air Cleaner Element
Calibration/Software
Exhaust System
Induction System"

But the procedure also includes going through steps to test the stock components - leading to identification and correction of the cause. Here are some examples:
"B75C Multifunction Intake Air Sensor - Contamination of the measuring element / Skewed / Water intrusion
Q17 Fuel Injector - Restricted >> Refer to: Fuel Injector Diagnosis
Air Cleaner Element - Incorrect / Missing
Engine - Vacuum leak
Evaporative Emission Canister - Cracked / Leaking / Visible Damage
Exhaust System - Leaking / Missing components >> Refer to: Symptoms - Engine Exhaust
Fuel - Contaminated / Poor Quality >> Refer to: Alcohol/Contaminants-in-Fuel Diagnosis
Fuel level - Low
Fuel Pressure - Low >> Refer to: Fuel System Diagnosis
Intake Manifold - Vacuum leak
Intake Air Duct - Cracked / Leaking / Loose Clamps / Visible Damage
Oil Filler Cap - Leaking / Missing
Positive Crankcase Ventilation System - Incorrect connection / Leaking / Restricted
Vacuum Hoses - Incorrect connection / Kinked / Leaking / Restricted"

 

A shout out to @ParagonPerf-Graham for the excellent customer service in handling something for which they were not responsible.

It also now makes more sense for the day that I saw smoke coming out of the hatch vent. It was the oil from the can that fell and covered the exhaust with pipe with oil.

I sent this message to Paragon and they have overnighted a replacement piece for the catch can.