Code P0153, P0171, and P0174 on a 1998 Mazda B4000 v6

So my truck recently failed its state inspection.

The car's computer was giving up three codes:

P0153 (Oxygen Sensor Circuit Slow Response [Bank2, Sensor1])
P0171(System Too Lean [Bank 1])
and P0174 (System Too Lean [Bank 2]).

I did some research into what that meant and how to fix it, some of the best information I found was on this forum. However, I have very little experience under the hood of a truck. My previous car was a little subaru that was extremely low maintenance. After some thought, I decided to get quotes from a couple of mechanics before I tried anything on my own.

I took the truck to a local Midas. They wanted to swap out both oxygen sensors to fix the issue. They also wanted to charge me $415 for the priviledge. (This was after they forgot what I wanted all together and called me up with a quote for a transmission flush.)

After that I took my truck to the nearest Mazda Dealership. Unfortunately, my Mazda just passed the 95,000 mile mark so it no longer qualifies for its emissions warranty. They want to charge $95 just to look at it, $95 for the actual work (if they decide that the oxygen sensors do in fact need to be swapped out) and $140 per sensor for parts. That comes out to a total of $470 dollars!

Are my expectations unreasonable? From what I can tell, the part costs $70-$80 dollars and SHOULD take about fifteen minutes to swap out.

I'm a college student, so money is really tight. I'd rather NOT break my truck, but I can't afford to pay that kind of money.

Well parts are often cheap and although I'm skeptical that you're competent enough to change them out in 15 mins! (you said yourself very inexperienced). You're forgetting that door rate at shops is really not the only thing to focus on or price of labour for that matter! To me I'd suspect you either have 02's causing the 3 codes or another issue like a vaccum leak, MAF etc, causing the lean codes and the 02 is also failling!
Finally nobody enjoys paying for auto repairs but unfortunately we all have to! If you can't afford it you shouldn't be driving! Peoples priorities always seem to be other places. I know you're a student and it's tough enough to pay bills on a student's budget sometimes but lots of students can't afford to even own a car or gas or insurance so I guess you could be considered luckier then them! n I'm not trying to rip on you just don't lose perspective!

Well, im sorry to disagree with both of those shops diagnosis. If the O2s were the problem, why isn't htere a code for the other banks o2? Obviously the O2s need replacing for maintainence reasons, but as to the cause of P0171 and 4? I doubt it. Look for a vacuum leak somewhere and check fuel pressure reading. Watch fuel trims when you drive it. Changing O2 sensors may fix the 1 o2 code, but not the lean codes.
In my humble opinion.

I humbly agree ^^

me 2

po171 & 174 are NOT caused by a O2 sensor problem. For the computer to spit out lean codes the o2 sensors need to be working. As far as the B2S1 slow to respond code goes look for a vac. leak on the bank 2 side. Upper & lower intake gaskets have been a comon problem. Sometimes the leaks might only show up on a cold engine. I have also seen a few with injector oring vac. leaks. Good luck.

I think they're gone! It has been 2 months!

Yeah, I think that's pretty much what we said 3 months ago.