Honda Rancher 420 - OEM Oxygen Sensor - 36531-HR3-A21

Thanks for that info, very helpful! I just bought a pair of ‘16 TRX420’s with EPS, barely broken in. And before I had a chance to ride either of ‘em, I’m now getting code 23 on both.

I measured megaohms / open circuit across both white wires on the heater circuit of the sensors on both units, so thanks to your info I know I need to replace them. A handful of short run-times to move, load, unload... I suspect condensation finished ‘em both off.

That said, any idea if the heater in the superseded part number is more durable? I couldn’t find any complaints of ‘18+ models with code 23, which I hope is a good sign.

I’m starting to second guess selling my trusty ‘00 TRX350FE, after seeing it’s not a rare issue.

Yeah, I’d found how to clear the codes. I used a jumper, seemed to have success as I got the flashing, but the code came right back / remained.

Which makes sense as the ohmmeter proved the heaters are open circuit.

Going to grab a couple new O2 sensors and get these quads sorted out. I went for a ride yesterday, and almost all of my doubts are gone.