Error Code..at a loss

The code pulled doesn't have anything to with sensor 2 down the shaft. I'm at a loss as the what it could. I've searched the net through and changed all the parts that are said cause this code to show.

 

^^^^^^^^^^^^ this

 

check your fuel pressure. As a fuel pump goes out, the pressure will drop. I am not certain of the fuel pressure but I think I remember 40psig, as it drops, intermittent lean conditions will happen.

There are two possible causes. The worst is the fuel pump, which is not cheap. The second is the fuel pump relay. I've chased down a couple of these problems where the relay contacts have higher-than-normal resistance. That lowers current, which lowers the pump motor power output. I'd always start with the pressure. I don't know if Toyota included a schrader valve on the fuel rail or not. Most manufacturers do, but some require a t-fitting. Whatever, this is a good first step.

Based on what you have done so far, this would be my most likely candidate.

 

P0171 is a lean reading on bank one. This is the side of the engine with cylinder #1. It is possible you have a vacuum leak (before the oxygen sensor)on that side possibly the intake gasket or even an exhaust leak at the manifold. A rare occurrence would be the fuel rail on that side getting clogged. The key is that you only have the one code. If you have both a 171 and a 174 then you would look at anything that affects both banks (MAF, vacuum hose, cracked intake boot, etc.). If it were an injector leaning out then you would be getting misfire codes for that cylinder. A little involved I know but I hope this keeps someone from just throwing parts at a problem.

 

Any updates on this? I have same issue.

 

Gas cap..... just throwing it out there...

 

so toyota code p0171 means that the right side (passenger side) O2 sensor is reporting too lean of a situation. and i do mean ONLY the passenger side exhaust. driver side works just fine. so air is getting in, not between the air filter and the engine, but where the air splits off to each head at the intake manifold. so here's a small list of issues that could pass air into the passenger side head and cause this fault code, IF it isn't a bad O2 sensor!

crack in the intake manifold at the passenger side head.

loose intake manifold.

bad intake manifold gasket

cracked intake port of the head

cracked intake valve(s).

bad cracked spark plug

lose spark plug

bad or cracked injector

lose injector

Now, aside from all of these, keep an eye on your coolant levels and engine oil levels. if your losing either, you may have some internal head or gasket issues though VERY unlikely.