O2 sensor code

krazyboi said:

The other day my check engine light came on and I took it to get the code read and it came up with P0174 "Fuel Trim Bank Two Condition-The ECM has detected a rich or lean air/fuel ratio condition on engine bank two. The fuel system for bank 2 was too lean."

The car has 140k and I haven't replaced the O2 sensors-I'm thinking its one of the 2 up front. Does anyone know if it is indeed the front ones causing the code (versus the back ones)? I plan on replacing them both and want to make sure I get the right parts.

Click to expand...

What makes you think it's the sensor.. it could be the sensor but most likely it's not.

that code is a condition code that indicates the fuel trim for that bank went over +25 percent..

First thing you need to do is to look at live data with a scan tool and see what the long and short term on bank one is and compare it to bank 2

You might have a p0171 bank 1 lean pending that has not set yet..


If you get your hands on a scan tool and you add the short term and longterm trim up on bank 1 and they are over 13 percent or so then it's probably not a sensor problem and you need to look into what can cause both banks to run lean.. things such as a vac leak or low fuel pressure or a bad maf can cause that.

if your fuel trims are high at idle and drop when you raise rpm's you most likely have a vac leak..

If they are normal at idle and climb with rpm's and load check fuel pressure..


If bank 1 is normal but bank 2 is running leak you need to look at what can cause one bank to run lean and the other normal..

Stuff that can cause this are.. Bad injector, misfire on one bank, exhaust leak near the upstream 02 sensor on that bank. a faulty 02 sensor..


typicaly when the PCM thinks the sensor is bad it sets the 02 sensor slow to respond code. p0153


Considering your mileage it could be a bad sensor but you need to check this other stuff..


BTW bank 2 is the passenger side bank and the sensor would be the upstream or the one close to the engine.