Codes p0171 and p0174

[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!

[Kenny]

I replaced my O2 sensor with a Bosch over a year ago and all is still well.
It's a very easy replacement job, though the electrical disconnect can be tricky to get at. I think it was snapped onto the frame with a tab...

I would also take a look to make sure ALL your sensor plug-ins are secure on your intake (I think there are only two on the black plastic body). One came loose on me last year and gave me all sorts of fuel codes.

[Triathlete]

Cleaning the MAF seems to have fixed it. Day 2 and still no light! Pased emissions test with flying colors!
I will put the O2 sensors on my list of things to do though since they are probably about due.
I crawled under the VX last night and they look pretty easy to get to.