p12 installed -> immediate CEL code 41 - bad ECU?

[jszuba]

Hi guys... I just got my p12 from the US. It came from a 94-95 Prelude AT.

I installed it in my '92 F22A2 4dr Exi which came originally with a pt3.

10 sec after I turned the engine, wham - there is a code - 41. Oxygen sensor heater something....

So I plugged my pt3 back in and... no CELs. Car runs ok.

So the question now is, is the ECU bad (I'd be F'ing mad coz it'd mean a return to an ebay shop...) or is that a sign of an upcoming O2 problem?

Is there a way of checking if an ECU is good?

[Gotz Cb7]

Our ecu's hate telling us our oxygen sensors are bad. Maybe the p12 is better at telling us when the o2's going bad. Also, did you take the negative off the battery, pull the ecu and backup fuses before installing the p12? The codes could still be stored in the p12 from whoever had it before, if that's even possible with it being unplugged already?

[SleeperSEDAN]

after its unplugged for so long it forgets the codes so thats not it. it probably is a bad or weak 02. you can force the code to be erased and see if it pops back up... are the ecu pins themselves all straight and such. like going into the clips normal

[deevergote]

If your o2 sensor hasn't been recently replaced, I would replace that first.

It's not likely that a bad ECU would only give an o2 sensor code. A bad ECU usually just shows up as a solid CEL. Checking to make sure the pins are all straight and undamaged is very good advice, though.

[jszuba]

Guys, your words are like music to my ears and honey on my heart...
I just spent a whole load of dosh on this + shipping to the UK.

Gotz Cb7:
I pulled the neg. terminal before even attempting to take the pt3 off. Thanks for reminding me and anyone reading this - never too many times a reminder!

SleeperSEDAN:
kind of scared to put it back in now (ie after pulling it out to reset + get home on the pt3). I sure hope it is the O2 sensor then. But why would pt3 not show this? Any idea?
Also, I tried to pull a code afterwards on the pt3 - A steady CEL came on for a coupe of seconds, and went off completely.
Oh, the pins are fine and went in smoothly upon installation.
It is only a little... weathered around the casing though.

deevergote:
the O2 sensor wasn't replaced recently, if ever...
I AM getting horrible mileage around London where I am currently. But I always thought that was because of the lousy traffic cycle... 30mph - 0mph - 30mph - 0mph.

[SleeperSEDAN]

hmmm... well i would possibly just check it out... my pt3 is super sensative but my pt6 isnt... like my buddies pr3 runs without cels and has no 02 sensor... sometimes things act up.

[jszuba]

You mean the O2 sensor?


The question about checking the state of an ECU is still hanging in the air though... take it to an authorised Honda garage?

[Gotz Cb7]

I AM getting horrible mileage around London where I am currently. But I always thought that was because of the lousy traffic cycle... 30mph - 0mph - 30mph - 0mph.

1 sign of bad gas mileage, is an o2 sensor. When mine went bad, I was gettin' around 160-180 to the tank, instead of my good ol' 260-300. My cel would only pop on here and there, first a code 41. Then a 1 and 41. Finally, when the CEL stayed put and didn't go off, it stored 1, 41, and 43 (fuel supply).

[Gotz Cb7]

Like Deev said, if you try to pull a code from a bad ecu, it would be solid. No blinks when pulling the code(s).

A bad ECU usually just shows up as a solid CEL.

[jszuba]

I'm going to probably change out the O2 sensor first.
I figured that since it is old and I had to change my TW sensor a year ago after it kept going bad for two years, the O2 might be in a similar state....
And hopefully, like you said... maybe the pt3 sucks at telling when the sensor is going, and the p12 does it so much better.
Though Europe being Europe, Honda is asking $255 for one...
I so envy you guys for having such cheap parts in the US

PS - Euro driving is a fuel consuming hobby :P
Around Kraków I get 400km/tank (250mi), around London I get 350 (218mi) at best...

[Gotz Cb7]

I got mine from Carpartswholesale.com. 80 bucks for a Denso (recommended by many), bought + shipped.

[jszuba]

So, finally after a week off ill, I got down to checking out if the O2 sensor is really shot. Of course I read my Haynes, and a 1991 service manual.
I pop the hood and... I don't know what I'm looking at... anybody know which plug is the O2 sensor?? None of them have more than 2 wires going in/out...

Here's a pic.

[visualpoet]

The o2 sensor is the only thing on your exhaust with wires going to it. Either right at the exhaust manifold or farther down on the downpipe. It looks a little like a fat spark plug stuck in your exhaust pipe.

[AbsurdNY]

I just wanted to mention, O2 sensors can be a bitch to get off. You might have to heat it up with a torch first.

[visualpoet]

I just wanted to mention, O2 sensors can be a bitch to get off. You might have to heat it up with a torch first.

And get an o2 sensor removal tool. They make a HUGE difference.