2000 Accord Coupe F23A4 ULEV engine.

Replaced the exhaust manifold and threw a CEL code.

After looking over parts, it appears the ULEV model has a different primary sensor than the LEV model. I'm curious what effect is of having an exhaust manifold similar to the LEV design on an ULEV motor.

This being said, the code points to something different.

P0141 - Bank 0 Sensor 2 - Secondary Heated Oxygen Sensor (Sensor 2) Heater Circuit Malfunction

I was careful when handling the sensors, but didn't remove the secondary sensor, only unplugged it. This could be just a loose connection from the plug I disconnected, but any other ideas out there?

 

Ah I hate the F23A4, its so sensitive to anything you do to it. I had the same problem on mine and I got rid of it by clearing the code really early in the morning when the car wasnt driven all night and it was cold. It hasnt came back since then.

Everything is ok, its just the sensor isnt sending the right message to the ecu. Unless it was damaged somehow but the way you described it I dont see that as problem.

 

I had a similar problem with my Accord once... I unplugged the secondary O2 sensor when I was replacing my cat, but apparently when I unplugged it the pins inside the connector came loose. Coincidentally, I ended up with the same exact code, P0141.

I can only suggest looking over the connector for loose pins/connections.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by philadd &raquo;</TD></TR><TR><TD CLASS="quote">I can only suggest looking over the connector for loose pins/connections.</TD></TR></TABLE>

That's my only option at this point. I'll get under it tonight and pull it out to check the pins. That's the only thing i can think of that could be wrong at this point, as unlikely as it sounds.

Phil, you say double checking the connector and pins fixed the issue?

 

The 2 black wires should have 12 volts when the key is on.
And 10-40 ohms resistance across the heater circuit of the sensor.

FWIW there is a service bulletin on ULEVs for the guys up north at the dealerships, not to open the hood outside in winter because the temp change over the engine will cause codes;
Talk about a picky system

 

Loose plug FTL!

hondadude, are there specs to look for to test an O2 sensor incase one is suspect in the future?

 

Well you really need to see the voltage swing of the primary sensor, and the voltage stability of the rear sensor.

I hook up my palm scan tool and hold the RPM at 2000, looking for .5 volt to .7 volt steady on the rear sensor; then .2 to .9 volt swings on the primary sensor.
I guess a guy could hook up to the green and white wires with a multi meter, but not sure if you could really get a good reading on the primary.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by AFAccord &raquo;</TD></TR><TR><TD CLASS="quote">Phil, you say double checking the connector and pins fixed the issue?</TD></TR></TABLE>

In my case, yes, I just fixed a pin that had come loose from when I unplugged the sensor. It's worked fine so far, and that was a little more than a year ago.

I remember watching (a.k.a. supervising) a friend of mine change out his exhaust, and he unplugged the secondary O2 sensor for some reason unknown to me. When he did, half of the pins fell out the back of the connector. He swore he was careful and only pulled on the connector itself and not the wires...