What code does bad gas cap seal set? Symptom: Erratic idle

Question

Erratic idle: sets code p0171: replaced/repaired every symptom for code p0171. Still erratic idle @ op temp. Major problem: code will not go away. Also, possible slight miss at tail pipe during periods when idling smooth. Help!

Answer 1

Hi there

A bad seal on the gas cap will usually set a p0455 code for an evap leak.

The P0171 code can be the result of a bad O2 sensor and several other items. I have also seen it happen due to a weak fuel injector as well.