How to fix Code 171 only on freeway driving in my Subaru Outback

Question

The check engine light comes on when I have driven on the freeway then stopped, turned off engine,  then resumed driving for about 5 miles. If I stop and reset the ODB (always code 171) , then drive 100 ft., then turn off and restart car I can go off down the freeway again without the check engine light coming on. This sequence has been repeated at least 20 times. Dealer can't find problem.

Answer 1

Hi there,

This is a lean fuel mixture condition on bank 1. This can be caused by a few things, first intake vacuum leaks will cause this, a fauty A/F sensor or possibly the mass air flow sensor. These are the most common causes.