"Frank van Hoof" <thehoofies@sympatico.ca> wrote
> I have a check engine code P0135 in on my 98 Civic, which is supposed to
be
> the primary oxygen sensor heater.
>
> Is this the oxygen sensor nearest to engine - just in the top of the
exhaust
> manifold, or the one further down?
>
> Any comments on aftermarket Oxygen sensors?

From general reading and rough recollection, buy only OEM.

Before buying, get a manual and go through the procedure for diagnosing this
code. Codes don't necessarily identify that a component like the O2 sensor
has failed and needs replacement. Could be just a loose wire somewhere. Have
you other symptoms of a failed O2 sensor (like inappropriate engine
revving)? Bad fuel mileage?

I found an OEM one that was a steal at https://www.automedicsupply.com/ .
Put it (a Denso, which is OEM) into my 91 Civic last year. Yours appears to
go for $70, tops, at this site. Goes for over $150 at Majestic Honda parts
online.

OTOH, I wouldn't say you are throwing money away by replacing a seven-year
old O2 sensor. I've read they do degrade in performance over time, though
mine lasted 13 years and may have been able to go longer.