denbill

Installed new mass air flow sensor, new A/F ratio sensors (both banks) and the B1S2 sensor. Yes, I used Denso on the up & downstream sensors. 0171 & 1153 show as pending codes. After replacing both A/F ratio sensors was only showing P0171. That is what led to replacing the downstream sensor. Now that it has been replaced getting the pending code for the B1S1 that I replaced 2 weeks ago. Over the course of the last 12 months, I have replaced all coils, plugs, OCV, knock sensors and harness. Gas cap is aftermarket....could that be the P0171 issue? Ready to take it to the scrap yard, so any help is greatly appreciated.

Lexusfixer

I am going to guess that you might have a clogged catalytic converter, the one in the front of the vehicle. Pull the sensor out and start the vehicle, if you have a ton of exhaust trying to escape the converter is probably clogged. I had this occur on my own vehicle with about 175k on the motor.


Second option is to pull the front converter off and inspect it, or get a vacuum gauge like this.


http://www.toolpan.com/ATD-Tools-565...23_a_7cATD5657


Follow the instructions, not that you will need any since the gauge is self explanatory . Just hook it up to a good vacuum source and read the gauge at idle and when applying the throttle.


Keep us posted.

carguy07

Cracked exhaust manifold?

denbill

Thanks. Hadn't considered the cat....well not for a few months. I ran cat cleaner through it twice a few months ago, and more recently fuel system cleaner. Not experiencing any kind of stall, sputter, etc. It actually runs very smooth with no typical "bad cat" odor. Mileage is at 192k. Been chasing this lean bank 1 code for a while now. Will follow your recommendations and see what happens. Thanks.

denbill

Checked intake manifold for cracks/leaks, but not exhaust due to codes. Will check that too. Thanks

salimshah

I would not act on any pending codes. Wait for them to clear out or become error codes.

Salim

denbill

UPDATE: Found exhaust leak in front exhaust pipe flex connector. Have ordered front exhaust pipe replacement. Once replaced, will update with whether that cleared the p0171. As of right now the pending p1153 has resolved and is just showing confirmed p0171.