90 accord stalling, code 41 43

I had some lean stalling on the interstate then the computer threw a
code, and everything was fine after that for few hundred miles. The
code is 41 and 43. 41 is listed as O2 sensor and 43 as lean mix. Is
the lean mix the cause or the effect of the O2 sensor code?

 

So I'm still stuck with the code 41, after replacing the O2 sensor and
recetting the ECM.

I measured 13.39V across the heater at the open end harness, and a 10
ohm resistance of the O2 sensor. The replacement is a Bosch...

This is an EX where the O2 sensor is in the exhaust pipe.

I'm stumped.

 

Get that Bosch sensor out of there and put an OEM sensor in its place.

 

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If you search this NG, I recall more than one person who tried multiple
sensors from bosch, then put in a good OEM and solved the problem.

'Curly'

 

For a code 41? The circuit seems fairly "dumb" so it's hard to
imagine what could be Bosched in it. The previous OEM sensor was
throwing a code 41 too..... the difference that I see is that the OEM
reads 16 ohms and the Bosch reads much less... but code 41
nonetheless. It's expensive to play part swapping with these things
because they don't take returns.

 

??? that won't make a difference? besides, this is a single wire
sensor - what are you testing with the ohm meter - it's not the heater
circuit because single wire sensors don't have one.

indeed. that's why people that have experience pay once for the oem
sensor, not multiple times for aftermarket. if price is the issue, go
to a junk yard - you can often pick up nearly-new oem sensors dirt cheap.

 

It's a four wire sensor. Heater, heater ground, signal, signal
ground. Supposedly isolated from the chassis too since it has a
separate signal ground, but that's probably worth a check next time
I'm under it.

Why would a junkyard sensor be nearly-new? A good idea, anyway, I'll
grab me a few more to play with.

 

You should not have a 4-wire sensor in that car. You should have a single-
wire sensor.

You've either got the wrong engine and/or ECU in there, or the wiring loom
has been hacked about to provide the grounds and feed for the heater on a
later-model sensor. Either way, it's might be wise to look elsewhere for
your ostensible sensor problem.

Have you considered that the sensor may have the wrong electrical
characteristics for the ECU it's married to?

 

It has a 4 wire harness. Look it up on any parts site if you don't
believe me (this is an EX, it's not a sensor that goes into the
manifold, it goes into the top of the down pipe). It worked at one
point... then we fixed a burned valve, then after I saw the code 43
(which I haven't seen since, nor have I experienced the sputtering/
stalling that happened on that one road trip), the OEM sensor started
throwing a code 41... and now so does the new Bosch.

Yeah, but I don't know where to look. The only thing I could have
come up with is that the OEM sensor shorted to ground on the heater
and blew a fuse. But as far as I can tell from the wiring diagrams,
the fuel injectors are fed off the same supply, so if the fuse was
gone (tested it anyway, it's good) then the injectors would have no
supply. Then I made damn sure by checking voltage at the pig tail
with the ignition on, sure enough, there's battery voltage there. The
thing is, the code 43 and 41 showed up at the same time to begin
with. So it's possible that something went screwy with that circuit,
shutting off the injectors which threw the 43 lean downstream code at
the same time as interrupting the O2 heater circuit. But I can't
fathom what event would do that...

Yes. That's what I am trying to figure out to get to the bottom of
this. What in the world is the ECM measuring to determine that it's
time to throw a code 41?

 

OK, so I thought about it a little more, since the heater circuit
ground goes through the ECM, then it is probably measuring the current
through the heater. So an internal leak to ground inside the sensor,
or incorrect impedance in the heater would affect the current that the
ECM sees. Can you think of anything else to check?

 

OBD-II ECMs do measure current from the heater wire. That's how it knows if
the heater's malfunctioning. However, I don't know if pre-OBD-II ECUs
monitored the heater wire or simply provided ground.

I had a better look at the manuals I've got, and it appears my original
conclusion was wrong: Your car DID originally come with a 4-wire sensor.

Corrosion at the connector, high wire resistance, I don't know what all
else.

If you post your question to the group rec.autos.tech, there is at least
one extremely knowledgeable and experienced technician (Comboverfish) who
posts there. He would be the best one to answer this one, as he has large
amounts of Honda experience.

 

three things:

1. if this vehicle is a 1990, as it says in your heading, then the
engine computer is expecting to see a single wire sensor. the only way
a 1990 accord would have 4-wire is if the vehicle has been converted for
some reason. and a 90 accord is not a typical candidate for that kind
of effort. if this is a 90 vehicle, and you think it's been converted,
you'll need to check the ecu's to be sure.

2. the two sensor types are very different in operation. you can't use
a broadband sensor, 4-wire, on a narrow band, single wire, ecu because
the output signals are not the same, even if you rigged up the heater wires.

3. many users here report dismal results with bosch sensors. including
myself.

bottom line, you can work with us by providing accurate information on
trying to figure this out, /or/ you can keep us in the dark and keep on
ignoring what people are telling you and see where it gets you. your call.

 

I did a better check of my Helm manual for that model. It did indeed come
with a 4-wire sensor. So did the Prelude, for that matter.

 

i stand corrected. i could have sworn i'd acquired a single wire sensor
from a 90 accord in a junk yard, but i must have been mistaken.

 

Everything else seems fine, so next step is to get rid of the Bosch.
It's still a mystery why the OEM quit working, but whatever.

 

they just do over time. sensor chemistry degrades.