Deciphering codes P0171 and P0325 - knock sensor?

I know that these codes P0171 System too lean bank 1 and P0325 Knock sensor circuit bank 1 are usually due to a faulty knock sensor and/or wiring harness. They can also be caused by some other components I believe.

The check engine light comes on under a heavy acceleration only, usually it lasts a day or two before coming back on.

However, is there a way to use a OBDB reader to pinpoint more accurately where the issue might be?

I've read that maybe the Fuel trim readings are a good place to start.

 

I have been dealing with a P0171 for awhile now, I have been told many many times that it is more than likely a vacuum leak somewhere. I have yet to find my "leak" but my truck is still running well enough.

What are your symptoms?

 

on 3.4's toyota uses a metal gasket for both the upper and lower intake... dont remember on the 4 cylinders, anyway, it is metal so that it will not suck through. If you have an aftermarket fibre type upper or lower there is a possibility that it has vacuum leak at either. Same thing goes for the throttle body to upper intake.
If the EGR system is not functioning as designed by either a broken vacuum line or blockage the combustion temps will be too high and that can induce a knock also. This is just one of those things that you are going to have to spend some time with.

 

Yea after changing the spark plugs it is running well enough for me to drive but I definitely need to find it because it is bugging me that there is something wrong. Hopefully this coming weekend I will retighten the bolts on the cat that I swapped and make sure that the gaskets there are sealing.

 

I also get P0171 after heavy acceleration or climbing grades. Once I clear it, it only appears again during the aforementioned variables. I think it's due to a dirty MAF, or a bad O2 sensor.