Codes p0171 and p0174

[Y33TREKker]

Bank One is the passenger side, Bank Two is the drivers side. (Bank One, Sensor One = before cat, Bank One, Sensor two = after cat. Bank Two, Sensor 3 = before cat, Bank Two, Sensor 4 = after cat). It looks like those two codes are telling you that both sides/banks are seeing lean conditions, so it's doubtful that O2 sensors on both banks would go bad at the same time, but stranger things have happened I guess.

They basically thread into bosses on the exhaust pipes, so removal and installation are relatively simple using an open-end wrench. The only specific requirement during installation is the use of O2 specific anti-seize for ease of future removal.

While it doesn't necessarily narrow things down much, other possible causes could be vacuum related issues with the intake manifold , the pcv valve, and/or the egr valve.

[Triathlete]

With both codes could it also mean the MAF is dirty or defective?

[Y33TREKker]

With both codes could it also mean the MAF is dirty or defective?

Yes. One of the P0171/P0174 diagnostic steps in the downloadable manual suggests checking the MAF sensor inlet screen for damage, or the presence of foreign objects which may partially block the airflow sample through the MAF sensor.

There's also another MAF diagnostic step that involves disconnecting the MAF sensor electrical connector so the vehicle can be monitored in "closed loop" mode, but it also requires a "Tech 2" analyzer (Isuzu tool?).

[Triathlete]

Thanks Y33. I think I'll do the MAF clean first...its the cheapest! I'll let you all know how it goes.

[Y33TREKker]

How long since the air filters' been changed? That could affect MAF air flow too. You never know, sometimes it's the simple stuff.

[Triathlete]

That was the first thing I tried 3 weeks ago...new K&N. Reset computer and it light came back on 10 minutes after start up.

I bought a $6 can of MAF cleaner, cleaned MAF, dropped a bottle of Lucas injector cleaner in the tank (just because it probably needed it anyways), reset the computer and went for a 20 mile test drive. So far no light. Will get my emission test done tomorrow.
After the holidayys i think I wil replace all 4 O2 sensors...suposed to be done every 100000 miles or so anyways...I'm at 110000!
Thanks again for all the help and suggestions everyone.

P.S. per the can of cleaner...your MAF should be cleaned every time you change (or would change for us K&N or Green filter guys) your air filter.

[Reg Hinnant]

O2 sensors not too hard to change. Getting to the wiring disconnects are the hardest part. I changed out all 4 of mine in a Montrose Colorado Auto Zone parking lot. At that point I knew vacation was over!