"Abeness" <news@nada.x> wrote
>> My 91 Civic's O2 sensor never actually failed. I just
>> chose to replace it pre-emptively based on something I
>> think Tegger wrote; the great prices at automedicsupply;
>> the drama of being stuck in the middle of nowhere (at the
>> mercy of god-knows-what charlatans) with a failed O2
>> sensor;
>
> Not to worry. From the Helm manual for my 1994 Civic,
> p11-39:
>
> >>>>
> ECM Fail-safe/Backup Functions:
> 1) Fail-safe function
> When an abnormality occurs in a signal from a sensor, the
> ECM ignores that signal and assumes a pre-programmed value
> for that sensor that allows the engine to continue to run.
>
> 2) Back-up Function
> When an abnormality occurs in the ECM itself, the fuel
> injectors are controlled by a back-up circuit independent
> of the system in order to permit minimal driving.

Oh yes; I'm aware that the only result of a failed O2 sensor
is a rough (very) running engine. I'm just particular about
driving a car like this for, say, 200 miles, or having to
pay OEM dealer price for a new O2 sensor when I'm on a trip!