Every scan tool is different.

Can you access the freeze frame data for each CEL you have? Can you post the engine parameters for each code you have?

 

I could only access the freeze frame data for the 0171; it unfortunately wouldn't let me view the 0141 or 2195 data for some reason (cheap Amazon scanner). So while it probably won't be much help, here are the results from the 0171 freeze frame:

• DTCFRZF: P0171
• Fuelsys1: CL
• Fuelsys2: N/A
• Load_PCT(%): 36.9
• ETC (degree C): 71
• STFT (%): 1.6
• LTFT (%): 18.8
• RPM: 1105
• MAP (kPa): 37
• VSS (km/h): 21
• Sparkadv (degree): 10
• IAT (degree C): 36

 

The intake air temperature sensor (IAT) seems to be reading 36C, which is 97F. Was the outside air temperature 97 F when the CEL last turned on? Double check that 36 is not in degrees F by hooking up the scanner and reading the IAT when the engine is cooled to the outside air temperature and see if the sensor is reading close to the outside temperature with the engine not running. Then start the engine and quickly look to see what value is being read by the IAT.

 

I changed the temperature units to degrees F. The freeze frame data did show 97F, but that code popped up just two weeks ago and it's been in the mid to upper 30's for the past few months. Could it be that 97F (36C) was captured at the time the engine was still running or warm?

I read the live data (and to be on the safe side, freeze frame) when the engine was cold, and the live IAT showed 37F (which was right around the outside temperature). Freeze frame stayed at 97F. I started the engine, quickly checked both the live and freeze frame (took about 10 seconds to scroll through and find each), and the results were the same; 37 and 97 respectively.

 

The freeze frame data is stored when the engine computer sets the check engine light, so I don't expect the values to change. The air intake temperature should not change drastically from the outside air temperature at any time.

The intake air temperature sensor is on the snorkel from the air filter box to the throttle body. I should have a 2-wire electrical connector. Unplug the sensor and look for any damage to the pins or any signs of corrosion (greenish/white crust). That 97 F indicates a flaky connection, a possible wiring issue, or maybe an issue with the sensor. Inspect the wiring harness for any damage due to the harness rubbing against a component.

A faulty intake temperature reading will mess up the calculation for air because hot air is less dense than cold air.

You may want to drive the car around and keep an eye out for a drastic change in the IAT sensor readings. Maybe wiggle wires/harness while the engine is cold to see if you can change that reading on the sensor.

 

Thanks! We're about to get blasted with snow today and tomorrow, so I'll take a look on Friday and report back.

 

Checked the connectors and harness, both looked fine. Upon further inspection, I did notice the air intake chamber was cracked/dry rotted. Any potential correlation with that?

 

That's a breather pipe that connects to the valve cover, so I'm not sure its enough to mess up the mileage that bad.

I can't tell if those cracks go all the way through, but that rubber boot is only a few bucks so you may as well replace it.

 

So sorry for the delayed response! Things have been quite hectic. I just wanted to follow up.

I gave up and took the car to the shop. They did a diagnostic, and said that both O2 sensors need to be replaced. They also found that the right rear seal was leaking oil all over which probably contributed. They also found a cracked left axle seal (they didn't mention if that contributed to it.) I had a similar issue a few years back (minus the P0141) and another garage just replaced the O2 sensor. The car wasn't THIS bad though. We'll see how it turns out!

EDIT:
I misheard them over the phone. After speaking with them in person (and also looking at the invoice), they replaced the right transmission seal because it transmission fluid, which in turn, caused transmission fluid to spray all over the O2 sensor. They only replaced the left axle because it was cracked. After parts and labor it was $550, which wasn't too bad.

(side note) Not sure if its correlated with another issue I've been dealing with, which was transmission fluid leaking constantly (had to fill the fluid every 500ish miles or so). I took it to two different shops, and they both told me that the seal was bad and "potentially" the differential bearing depending on the condition, and that the entire transmission would need to be rebuilt (which is obviously a ridiculously expensive job.)

 

Would be interesting what your MPG is next time you calculate it.