Hey Everyone,

I have a 2005 Pontiac Bonneville GXP with about 160,000 miles. I replaced my spark plugs on my car a few weeks ago, way overdue for a change. I now have the following codes:

P0174 - Fuel Trim System Lean Bank 2

P0171 - Fuel Trim System Lean Bank 1

I don't know if these codes appeared immediately after the spark plug change. The reason for this is I've had an emission control code for years that I can't fix and because of this I didn't check the codes right away.

Before I go out and buy new sensors I wanted to ask if it is possible this is related to the spark plug change? I find it strange that both banks are reading lean. If it's just a coincidence that's great, I'll grab some O2 sensors and a mass airflow sensor and see what happens. If its because of the plugs, or more likely, because of something I may have done, please let me know before I start spending money.

Thanks!