02 sensors can be bench tested with a propane torch and a multimeter. I think there are YouTube videos after showing how to do it.

I see you are fairly new here so I don't know whether or not you have a scan gauge or an altar gauge in your truck. Filter gauge could be set to show O2 sensor voltage readings.

And yes, and O2 sensor failing after only 19,000 miles is disappointing but not unheard of. I have no idea why they fail in our trucks as early as they do but through the school of hard knocks I have been become quite adept at replacing them.

 

Scan gauge was the first thing I bought, I'm a big fan of instrumentation and was appalled at the factory temp gauge scam. I'm pulling the upstream driver side sensor today, cleaning and checking; with a new one standing by in case it's needed. Will report back.
thanks all.

 

If you have leaking valve cover gaskets the leaks can drop on the electrical connectors of the O2 sensors and the main wiring harness. I went through two sensors prematurely (same side) before my helpful local Indy Rover shop told me to stop using the clip harness and hardwire the O2 sensor right into the main harness.

I cut the easy connect portions off the ends, crimped the wires together and sealed it up with heat shrink tubing plus a good wrapping of electrical tape and I've not had another one prematurely fail.

They are a bit harder to unhook when you need to remove the exhaust pipes for any reason but it's a pretty bullet proof set up.

You might want to check out your valve gasket covers for leaks. It doesn't take much oil to foul the connectors.

Anyway, just my two cents.

I'll also throw in a plug for the Walker O2 sensors from Rockauto.com over the Bosch. Seems like a lot of people had issues with the Bosch ones lately from various sources and the Walker ones are the "it" sensor of the moment. Personally I have two Walkers pre cat and two Bosch post cat so your mileage may vary.

 

Thank you for posting this! I had the same issue on my '01 Disco 2, the throttle body warmer was leaking badly and the coolant trails led down to heavy staining around the O2 sensor on bank 1 just below the back of the engine on the driver's side.($260.00 Amazon) code reader showed misfires on 3,5,7 and 4 and no issue with the O2 sensor. I took a gamble and bought a new O2 sensor ($64.00) and bingo! Misfire on #4 was a loose plug wire. The engine had very low power and a studder/bucking at speed around 50 mph. Code reader also threw code for a bad ($20.00 Amazon). Replaced the TPS and inspected/replaced spark plugs on 3, 5, and 7 - they looked good but two broke trying to get them out. Truck is running awesome now with faults cleared, I hope this info helps someone else.