@Wompom
I just started having the p0172 code pop-up. What did you do to fix your issue?
I just threw 2 new o2s. While I haven't got the code yet since I haven't driven enough miles. however my AFR is still displaying sporadic AFRs. Mostly in the 10 to 12 AFR range and back to 14.6/7. I'm wondering if it's my ECT sensor no longer working properly. It'll be normal 14.7 for a few minutes and then drop to 10-12 AFR on idle with a normal warm operating temp.
Note...I got the CEL p0172 when my truck pulled off the freeway into a gas station after my last trip. It stalled on me and shut off and I coasted into the pump. I also had idle issue when pulling off the freeway and it would run rough.