Hey fellas, I'm hoping I can get some help on this. My car (2002 GT) has the codes P0161, P0171, and P0174. I did a little research and found what the codes are here: http://www.paladinmicro.com/pmicro.php#

But to be honest, I'm a bit lost and need some recommendations as to where to start interpreting these codes. Is there a way to test o2 sensors? Should I start by replacing the oxygen sensor/s? If so, which one/s? Are these codes common together or am I dealing with more than one problem?

A little history on the condition of the car... This is my summer driver, I use it for work during nice days, but otherwise just sits in the garage and stored during winter. It’s been running fine since it came out of storage, but a week ago it started with a looping idle. RPM's drop and rise and stabilize but it has a rhythm to it and only in idle. I cleaned out the IAC and that did not fix the problem. I also just removed my off road x pipe, and one of the o2 sensors was on very tight, so I also wonder if I yanked on it too hard and damaged the sensor. It was on so tight that the o2 wrench would slip and round off so I ended up using a set of channel locks on it to remove it from the pipe.

This car is basically stock engine, not tunes or mods.

 

There is a way to test the O2 sensors, click on the Testing a Platinum/Zirconia O2 Sensor? link on this page.

However the P0161 code is for a circuit malfunction on the driver's side rear sensor; the P0171 and P0174 indicate good sensors reporting a lean mix an both banks--check the possible causes, from top to bottom, from the list on my site...

 

Thanks a ton Cliff! I will go though the list and check each component. Hopefully it's something simple like the clip not all the way in on the sensor

BTW- that is a very clean SL500. I just recently purchased a German car as well, an 1988 BMW 535i. It's an E28 with the M30 inline 6. It's my first car outside of the domestic brands, and I have to say I'm loving the German engineering.

Once again- thanks for the help!