modifry

Monday morning I started the car and the CEL came on and stayed on. I have since driven 600 miles mostly highway with about 20 stop/start cycles, and the CEL is still on.

So I did some reading here and in the shop manual, and checked the code with the 'ole paperclip trick and found two DTC's:

6-3 (P0139) - Secondary heated oxygen sensor slow response
6-5 (P0141) - Secondary heated oxygen sensor heater circuit malfunction

I checked the sensor like the book says, and sure enough, the heater circuit is open. Is it safe to figure the slow response is because the heater is bad?

I have no intention of leaving the bad sensor installed (on my way to buy a new one now), but I'm curious what the ramifications would be if I left it installed?

I assume it will continue to give me the CEL, but the car should still run OK, right?

I'm guessing the heater is there to warm up the sensor during cold-start conditions? So if it's bad does it only affect cold engine operation, or is there something I don't know?

I also discovered the electrical troubleshooting manual incorrectly shows the connectors for the primary and secondary sensors reversed. I measured the "secondary heater" and found 3.3 ohms, exactly what the primary resistance should be. A quick trace of the wires confirmed the book has the photos labelled backwards.

Makes me wonder what else is wrong.

cdelena

I have yet to understand the function of the secondary sensor. Mine gets a low or high voltage indication on occasion and the car runs fine. I reset it with the OBD software and it is appears again (usually in conjunction with hitting a big bump) a month or more later. The sensor is expensive enough that I have just shopped for a used one (only found one deal but in never went).

jguerdat

Sorry but I wasn't aware of the paperclip trick. I used it on my Prelude and I'd like to know about this one. Care to share?

jerrypeterson

Yeah, it should be fine. I've been running on the same codes for almost a year now.

modifry

[QUOTE]Originally posted by jguerdat
[B]

Sorry but I wasn't aware of the paperclip trick.

modifry

[QUOTE]Originally posted by jerrypeterson
[B]

Yeah, it should be fine.

TwoFourty

You don't. BTW I think the secondary H02s costs $280. I am running without it for now.

jerrypeterson

You are such a pessimist. Besides, things normally make noise when they break. I mean, what good is a CEL when you already chucked the crank out the side of the block?

Seriously though, if having no CEL is preferable you should address the issue. Have you pulled the 02 sensor to check for catalytic converter debris? If a chunk of catalyst has broken free and lodged itself in the sensor it will likely diminish its performance. This scenario could potentially damage the secondary 02 sensor. Installing an 02 simulator would negate the need for the secondary 02 sensor all together and may be a good option if you have forced induction or a cat on its last legs. Otherwise you may end up buying a lot of replacement 02 sensors just to keep the big bad CEL away.

jguerdat

Cool beans! Thanks!!

modifry

[QUOTE]Originally posted by jerrypeterson
[B]

You are such a pessimist.