Navien Error while in lockdown (of course)

[Faderus]

I have a Navien NCB-240E that has been in place and working flawlessly for about 3 years. Now that I am under lockdown (NY State) it has thrown an E35 error code twice in 2 days. This error code E035 corresponds to a gas pressure flow sensor according to this site: https://www.tanklesshotwaterguide.ca/2010/04/navien-tankless-error-codes/.

Is there anything else I should check before I just order this $40 part?
Do I have to break any gas connections to replace it?
Are there any other likely culprits? I considered a short term interruption of the gas flow to the house (who knows what happens with skeleton crews staffing things) but don't think that is likely 2 days in a row.

I am not opposed to calling a plumber in general, but inviting people into my cocoon of apparently disease free air isn't high on my list of things to do this weekend.

 

[HydroAirJoe]

That is an easy part to replace on a NR-240 (I have one and did this myself). Not sure how much you have to do on a NCB to replace it but you don't have to disconnect the gas lines. Of course, shut off gas and power while working on it.

If you really don't want to call a plumber, I think as a DYIer it is safe to replace the GPS to see if your problem goes away. The tubes that connect to the GPS could have splits in them causing problems, You can check the voltages coming out of the GPS (hunt down a service manual online for the proper values). If it was me, I would do some basic checks like the tubes and connection (check the connection at the PCB).

If that did not work I would replace the GPS and the tubes.