I recently replaced a rear O2 sensor on my 98 5SFE engine. The check engine light went off within about a mile of driving. I then took it to a friend who is a tech and he erased the stored code from the ECU's memory. If he had not done this using the tool, would the code have eventually cleared from the ECU's memory? If so, what is the criteria? key starts? miles driven? time? Also, what would be the required number/distance/time for it to clear? Thanks for your input.

Mike

They would stay in the ECM long-term memory until power is disconnected.

http://www.autoshop101.com/forms/h46.pdf

Brain,

Thanks again for the answer and the link.

Mike