I have a 99 4Runner with the 3.4 V6. 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

 

Try cleaning the MAF(mass air flow) sensor, this is the most common source of that code......

Use the Search button, there are plenty of write-ups on how to do it......