Accord V6 CEL - upstream A/F sensor?
 

I'd appreciate some advice if you have experience in this area.

I have an '04 Accord V6 with 76,000 miles. Has been running fine, although gradually over the last few years the gas mileage has gotten worse. Now down to around 20mpg around town and maybe 26 freeway.

The Check Engine Light lit up. ODB code p2243 Rear Air/Fuel Ratio (A/F) Sensor (Bank 1, Sensor 1) VCENT Line High Voltage It went out by itself. Now it is back.

I'm trying to decide whether to just change the sensor, or pay to have a pro troubleshoot it. Seems like it could be a bad sensor, or it could be any of a number of things, such as fouled plug in bank1 , or bad coil in bank1, or dirty injector in bank1, etc. etc.

Also please confirm that Bank1 is closest to the firewall, Sensor1 is the "upstream sensor" (accessed from on top in the engine compartment), and that a Denso 234-5010 would be the correct OEM replacement.

Bottom line - would you "plug and pray" or would you have a pro troubleshoot?

Thanks,
Bill