P0172 Scion -

Question

Drives fine. idles rough on occasion. starts rough on cold days...takes half hour or so until it sounds normal.

Answer 1

Hi there,

This code is for a rich fuel mixture. This can be caused by several different things. The most likely would be the front O2 sensor. However a bad fuel injector and a bad fuel pressure regulator, as well as mass air flow sensor can cause this code.