1994 Civic EX 5MT: DTC 41 (O2 sensor heater)

Hi, folks. Haven't been here in a while. Combo of excellent previous
advice here that got me through a couple of repairs, plus the first baby
in the family--boy now 5 mos. and super cute!--and a move. ;-))

Anyhow, my MIL (check engine light) indicates a DTC 41. 128K miles.
"Primary oxygen sensor heater." Cleared and confirmed. [Thanks Tegger
for caching that excellent OBD I code retrieval PDF.] I haven't yet gone
through the testing procedures in my Helm manual--still gotta find my
meter after that aforementioned move--so I won't be replacing the O2
sensor before that, but I'm curious: I saw a post from Randolph from
back in 2003 that suggested success with a generic aftermarket sensor.
Is OEM is any better than aftermarket in this case? I stick with OEM for
mechanical stuff. Can't say which is there now, or whether it's ever
been replaced; I bought the car used.

If it turns out that I need the O2 sensor, I don't terribly mind $182
for the one he
http://www.hondaautomotiveparts.com/...NIFOLD+%282%29
It will save me a splice on stainless steel wire. Here's hoping it's
merely a dirty connection...

Here is a little info on my O-2 senser heater saga. About 5 years ago my
O-2 sensor heater went out at about 150K miles on my 95 Civic EX. After
confirming the heater was burned out with a multimeter, I replaced it with
an OEM unit from Manchester Honda for right around $150. Four years and
40K miles later, same problem. Ok, time for some different strategy....I
went with a Bosch senser wired with the correct connector that fit
perfectly. I purchased it for $100 from NAPA with a lifetime warranty.
It's been working very well for the past year. I hope I'm done paying for
O-2 sensers. Cheers.

duckbill wrote:
> Here is a little info on my O-2 senser heater saga. About 5 years ago my
> O-2 sensor heater went out at about 150K miles on my 95 Civic EX. After
> confirming the heater was burned out with a multimeter, I replaced it with
> an OEM unit from Manchester Honda for right around $150. Four years and
> 40K miles later, same problem. Ok, time for some different strategy....I
> went with a Bosch senser wired with the correct connector that fit
> perfectly. I purchased it for $100 from NAPA with a lifetime warranty.
> It's been working very well for the past year. I hope I'm done paying for
> O-2 sensers. Cheers.
>

Thanks for the report, duckbill. Found my meter and tested the
sucker--sure enough, my sensor heater is burned out at 128K miles. Bosch
sensor is $81 at napaonline.com, but I don't see anything about a
lifetime warranty--how'd you get that on an O2 sensor? Autozone says 1
year. Since Honda OEM carries only a 1-year warranty as well, may as
well save $100+ and see how it goes.

After googling around a bit more I found a comment by Elle pointing to
http://automedicsupply.com, which has a Denso (=OEM ND?) for just $64.
They also have a Walker(?). Curiously, only a 90-day warranty is noted.
Can anyone relate their experience with these guys and how long either a
Denso or a Walker from them has lasted?

As for getting it out, I saw someone suggest a regular spark plug socket
(5/8"?), but how would I use that without snipping off the connector? I
don't care about the connector on the old one, but a combo wrench and PB
Blaster should do the trick to get the old out, right? Maybe also
running the engine for a minute or two to warm up the manifold.

"Abeness" > wrote
> Found my meter and tested the sucker--sure enough, my
> sensor heater is burned out at 128K miles. Bosch sensor is
> $81 at napaonline.com, but I don't see anything about a
> lifetime warranty--how'd you get that on an O2 sensor?
> Autozone says 1 year. Since Honda OEM carries only a
> 1-year warranty as well, may as well save $100+ and see
> how it goes.
>
> After googling around a bit more I found a comment by Elle
> pointing to http://automedicsupply.com, which has a Denso
> (=OEM ND?) for just $64. They also have a Walker(?).
> Curiously, only a 90-day warranty is noted. Can anyone
> relate their experience with these guys and how long
> either a Denso or a Walker from them has lasted?

My Denso O2 sensor purchased from the site above is still
going strong (on my 91 Civic) after 2.3 years, 31k miles.

Absolutely do not get the Bosch. Either Denso or Walker is
most likely the OEM sensor for your car. Don't let the fact
that this part is not coming from an "OEM dealer" throw you.

> As for getting it out, I saw someone suggest a regular
> spark plug socket (5/8"?), but how would I use that
> without snipping off the connector? I don't care about the
> connector on the old one, but a combo wrench and PB
> Blaster should do the trick to get the old out, right?

Borrow an O2 sensor wrench from Autozone. No charge,
overall. I think mine is 22 mm or 7/8-inch.

PB Blaster could not hurt.

> Maybe also running the engine for a minute or two to warm
> up the manifold.

Dunno.

That the OEM one from Manchester Honda went bad at 4 years,
40k miles is surprising. You sure you are taking all the
appropriate precautions with these? Getting any kind of gunk
on the probe will foul them, for one.

Elle wrote:
> My Denso O2 sensor purchased from the site above is still
> going strong (on my 91 Civic) after 2.3 years, 31k miles.

Good to know--thanks!

> Borrow an O2 sensor wrench from Autozone. No charge,
> overall. I think mine is 22 mm or 7/8-inch.

In NYC, I dunno about no charge... But ya know what? If the O2 sensor
wrench saves me from having to remove the heat shield, it's worth the
$10 automedicsupply sells it for even if I use it just once. I'm still
saving $100+ over getting the OEM from e.g. Majestic, *without* the wrench.

> That the OEM one from Manchester Honda went bad at 4 years,
> 40k miles is surprising. You sure you are taking all the
> appropriate precautions with these? Getting any kind of gunk
> on the probe will foul them, for one.

duckbill had the failed OEM sensor, not me. I'll definitely be sure to
keep the anti-seize off the sensor, though. Anything I should be looking
for on the inside when I have the sensor out? "Bad" residue or somesuch?

"Abeness" > wrote
> Elle wrote:
>> My Denso O2 sensor purchased from the site above is still
>> going strong (on my 91 Civic) after 2.3 years, 31k miles.
>
> Good to know--thanks!
>
>> Borrow an O2 sensor wrench from Autozone. No charge,
>> overall. I think mine is 22 mm or 7/8-inch.
>
> In NYC, I dunno about no charge... But ya know what? If
> the O2 sensor wrench saves me from having to remove the
> heat shield, it's worth the $10 automedicsupply sells it
> for even if I use it just once.

Absolutely. Buy the wrench from automedicsupply.

I forgot: This past summer I was going to buy an O2 sensor
wrench (for an exhaust manifold gasket replacement job,
among other uses, of course). Then I remembered I had
purchased a die grinder recently and also had a 7/8-inch
combo wrench kicking around. So I cut a notch in the closed
end of the wrench and, voila, I have a home-made O2 sensor
wrench.

Of course if the sensor is very tight, folks should use the
exact fit socket wrench. You should expect your 94 Civic's
sensor to be tight. IIRC mine was the first time, but not in
a god-awful way. I had the correct fitting Autozone loaner
wrench, and it worked fine, with maybe a little PB Blaster.


I don't torque my sensor to spec but go by feel (based in
experience at this point) instead.

> I'm still saving $100+ over getting the OEM from e.g.
> Majestic, *without* the wrench.
>
>> That the OEM one from Manchester Honda went bad at 4
>> years, 40k miles is surprising. You sure you are taking
>> all the appropriate precautions with these? Getting any
>> kind of gunk on the probe will foul them, for one.
>
> duckbill had the failed OEM sensor, not me.

Beg pardon.

> I'll definitely be sure to keep the anti-seize off the
> sensor, though. Anything I should be looking for on the
> inside when I have the sensor out? "Bad" residue or
> somesuch?

The sensor just juts right into the path of the exhaust
gases. Where it juts etc. should not look different from
the inside of the car's tailpipe, AFAIC.

I think you got your money's worth out of the original
sensor (14 years).

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; and some
suggestions on the net that my fuel mileage might improve a
tad (can't say it has; but it's certainly not worse,
either).

Elle wrote:
> I don't torque my sensor to spec but go by feel (based in
> experience at this point) instead.

Same here as far as torqueing by feel, though being new to an aluminum
block I did pick up an I-beam type torque wrench when I bought the car.
Will probably use it here.

> Beg pardon.

Hey, no problem!~

> The sensor just juts right into the path of the exhaust
> gases. Where it juts etc. should not look different from
> the inside of the car's tailpipe, AFAIC.

Inside of my tailpipe is pretty black with carbon deposits. I am burning
some oil, though I've never really pinned down how much. Not excessive
for a car of this vintage/mileage. I tend to drive pretty fast, but
generally don't abuse my engine with hard acceleration.

> 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.
<<<<

(I'd expect similar back-up function in any such system designed by
reliable engineers.)

I gotta say, the wealth of information, including troubleshooting
flowcharts, in my Helm manual makes it worth many times the $70 or so
that it cost me.

"Abeness" > 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!

Elle wrote:
> 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!

I hear you there. I actually haven't tried unplugging the sensor and
running the engine (right now it's just the heater that's burned out,
and the car is running reasonably well). Sure ran rough after I cleared
the ECM, though. Chugged like an old lawnmower for the first 30 seconds!
I'll try running it with the sensor completely disconnected before I
replace it and report back if I have a minute.

Abeness wrote:
> I'll try running it with the sensor completely disconnected before I
> replace it and report back if I have a minute.

Car runs fine with the sensor completely disconnected. Now, I haven't
yet reset the ECM, so will also try that and see if it's able to get
past the lawnmower chug stage on default O2 sensor values before I pop
in the new one.

If only I could get the old sensor out... I've sprayed liberally with
Liquid Wrench--will pick up some PB Blaster tomorrow--and tried running
the engine for a couple of minutes to warm up the exhaust some. I have
an O2 sensor socket, but am worried about rounding off the nut. I
suppose I could snip the wires and use a closed sparkplug socket to get
the old one out, but the O2 sensor socket seems pretty solid despite the
slot for the wires.

Since I haven't taken the heat shield off--those nuts are pretty well
rusted to death--I have limited tapping abilities. Any other ideas?