Help with an OBD code. '99 4Runner

[hodag]

I have a 99 4Runner with the 3.4 V6. 121,000 miles.

After about 150 miles into a roadtrip this weekend, the check engine light came on. This is the second time this has happened, both times after 150 - 200 miles of highway driving.

Both times I have gotten this same code when reading the OBD.

P0171 system too lean (bank 1)

The check engine light never comes on with city driving, only on roadtrips. Where do you think I should start looking? Bad gas cap would kick the OBD all the time, not just highway driving.

Im thinking vacuum leak or bad O2 sensor, but Im just not sure. Any help would be appreciated.

Hodag

 

[Jukelemon]

Bank 1/2 codes do tend to point to O2 failures. I am not sure if there are any other sensors that have both Bank 1/2 designations.

 

[2ndGenToyotaFan]

I was thinking the same thing, if it's only one side of the engine that eliminates a lot of things to check. Could be an injector on that side isn't operating properly. At 120k I'd change the O2 sensors anyway, unless they have been changed (most haven't....)

 

[hodag]

Thanks guys, Ive been told at Yotatech that I should clean/replace the MAF. Im a little nervous cleaning the tiny wires in there, but they assure me its easy.

Just trying to cover the bases.

Hodag

 

[Jukelemon]

Hmm, not sure why that would throw a bank 1/2 code i.e. why just one bank as opposed to both? The MAF controls intake for both sides of the engine.

 

[WristPin]

you need new o2 sensors.
NTK part number 24554