Welcome to JustAnswer.com! My name is DriveFast71(Ron) and I will do my best to answer all of your questions completely and accurately.
Do you happen to have the "p-code" associated with this? The Oxygen Sensor and Fuel Cap are in two seperate systems. One code with not be "either a fuel cap or oxygen sensor" - I'd like to verify your diagnosis, and if an Oxygen Sensor, determine which one- this vehicle has 4 of them.
Ok. P0141 is an Oxygen Sensor code. Nothing to do with the Fuel Cap what-so-ever (God Bless AutoZone employees....)
The P0141 is pointing to a fault with the internal heater for the Oxygen Sensor at Bank1, Sensor2. The on-board computer uses this internal heater to get the sensor to normal operating temps within a matter of seconds on cold starts. Inspect the electrical connector for any loose or broken wires. If the visual inspection checks ok, replacing the sensor should solve the problem. There is a special tool that will make the job a little easier: Oxygen Sensor Socket - which you can usually rent at any "big chain" parts store. This isn't a bad DIY'er job at all. This sensor is located under the vehicle, mounted to the exhaust.
Ok thanks for the answer, and the diagram. What about resetting the light afterwards?
The next time I have an issue, is there a way to get back to your personally? I have two teenagers with Honda Accords (2003) (2005) and it seems like once a mth Im doing something minor to one or the other. I've talked to some other JustAnswer guys that were not as helpful, so if I can use you for future issues I would like to.
While replacing the sensor, you should remove the "NEG" cable from the battery. This will ensure no electrical "mishaps" while doing the job, and it will also "clear the codes" from the on-board computer, resetting the Engine Light.
I do believe there is a "request" button somewhere on the Just Answer home page. If you cannot find it, simply use my name in your next question, and I will get it (use "DriveFast" as there are a couple of "Ron"s here!)
Glad I could help! Have a great day!