So, I thought I'd share a quick story and to document for the forum a simple engine fault and quick fix.

Yesterday, I was driving the Bentley "aggressively" in Dante's Furnace, also known as Phoenix. It was 113*F (45*C). There were several moments when I was in PE (boost), then I got caught up in traffic and about 5 miles of stop lights and slow going. I looked down and saw the CEL. When I had a chance to try, I realized a lot of loss of power. Trans started downshifting hard from 2nd to 1st (right before a dead stop).

I got home wired up VCDS and pulled the following in addresses 1 and 11:





The 5 minute fix:

I gave it about an hour to cool down a little bit so I didn't burn my hands, but at 45*C ambient air temps, it wasn't much cooler...LOL

I pulled the air temp sensor, sprayed it with CRC Electric Contact Cleaner, wiped it down, put a small dab of dielectric grease on the O-ring, reinstalled it, cleared the DTCs and today, all day, car ran fine.

A little info about the IAT from my tuning side - For the most part, the IAT doesn't impact things much until ambient air temps are really cold or hot and start to cross over about 85*F to 90*F. Once air temps get this hot, the IAT becomes a primary sensor to the closed loop process. Over 90*F and in increasing increments, the ECU begins to pull timing. This is because the charge air mass is coming in too hot to maintain an aggressive timing advance. The hotter the charge gets, the more timing is pulled. Any performance guys out there know, this is the power killer and the offset is to install a meth injection system (but this is for another day, another thread).

From a lot of data logging, if ambient air temps are coming in the grill at 113*F, by the time that air mass reaches the IAT it'll be about 123*f to possibly as much as 130*F (dirty air filters exacerbate this air charge temp). In my case, and in that moment, I think my poor old tired air sensor just couldn't take it anymore and fainted from the heat (a younger IAT could have handled it). In the moment it did, and without that primary data input, the ECU said "That's it!" shut down closed loop, went open loop and on a fixed fueling table (which is ALWAYS pig rich for engine preservation) and recorded a P0175 before shutting down the trans and limp mode.

By the order in which I saw the P-codes in address 11, I knew right away, the IAT (P-3377) shut down first BC of the extreme temp and I knew it was the primary cause of the failure. The P-0175 was recorded second and was a result of the P-3377, not the cause. So, addressing the air sensor was all that was needed to "fix it", fix everything.

BTW, given temps were extreme, I could have just cleared codes and I'm sure I'd be in the same place today. The 5 minute cleaning was only to ensure it a little bit. I have ordered a new sensor. I found it for $21 USD. When it gets here I'll just swap out (another 5 minutes) and should be all better.

One last comment - the P1923 in address 11. This is NOT a fault. It only notifies the tech to look at address 11. It has been mistaken as yet another fault in the past, but simply let it go. Once the real problem(s) are addressed in 11, P1923 goes away on its own.

Hope this might help someone in the future.