Oxygen Sensor
Purchased 2008 v-10 Ford class A with 30,000 miles. Dealership replaced oxygen sensor before delivery. 800 miles later, check engine light is back on. Diagnostics determined another oxygen sensor fail...
Forum Discussion
The diagnostic should tell you which sensor failed. If you don't have a scan tool, they're fairly cheap. Also, spring for an o2 sensor wrench, they're well worth it!
