cbjfan2009

Hi folks, this is my first post here. I'm new to car repairs and am very green.
My wife's 2001 Honda Civic EX 5-speed, all factory-standard equipment, has had an SRS light and MIL for some time. I found out the SRS light was likely caused by electromagnetic interference with the OPDS sensor in the passenger seat. I reset that with the paperclip jumper method and it hasn't come back.
For the CEL/MIL I bought an Bluetooth OBDII connector and paired it to the "Torque" program to read the trouble codes. I got code:

<table class="one" cellspacing="0"><caption>P0141 - Generic</caption> <tbody><tr> <th>Type</th> <td>Powertrain - Fuel and Air Metering - ISO/SAE Controlled</td> </tr> <tr> <th>Description</th> <td>O2 Sensor Heater Circuit
</td> </tr> <tr> <th>Location</th> <td>Bank 1 Sensor 2</td></tr></tbody></table> or
<table class="one" cellspacing="0"><caption>P0141 - Honda</caption> <tbody><tr> <th>Type</th> <td>Powertrain - Fuel and Air Metering - ISO/SAE Controlled</td> </tr> <tr> <th>Description</th> <td>Secondary air injection (AIR) pump - malfunction
</td> </tr> <tr> <th>Cause</th> <td>Wiring, AIR pump relay, AIR pump, ECM
</td></tr></tbody></table>
http://www.dtcsearch.com/P0141/

I'll be honest, I don't know jack about car insides. But, I really want to start learning and fixing. I have Alldata 10.40 ("AD" from now on) at my disposal.
1) AD tells me to reset the ECM/PCM. This is accomplished by disconnecting the battery terminals for ~30 minutes, correct? If there's a better way, please advise.
2) AD tells me to start engine after reset and observe for the DTC. I will do this after someone has indicated the best route to reset the ECM.
Thanks a tons folks.

ezone

There is no AIR system on these cars.

P0141 is for the rear O2 sensor, the one furthest away from the engine in the exhaust stream, the one located in the middle of, or after the cat.

You just need to erase the code, you don't really need a full PCM reset. That involves setting learned values set back to zeros (fuel trims and idle program) and you will probably need to do an idle learn procedure. (Some scanners do the full reset when you clear codes though, no biggie.)

See if your Torque app can clear codes. (If it can read the codes, I'd hope it can clear them too.)
If not, the the battery disconnect can clear them.

The light and code will come back about 5 seconds after starting if the fault is still present. (it will be.)
99% just need the sensor replaced.

Use OEM parts. If the sensor was made by NTK, use the correct NTK. Same for DENSO, use another DENSO.
Bosch has no place in these cars.

ezone

If you have a locking radio, make sure you have the unlock code before you disconnect the battery.

cbjfan2009

Thank you very much for the reply. I was going to question about the AIR system, but I just read up on it through wikipedia for a basic understanding. I read numerous posts around the net indicating the post-cat sensor is usually the culprit, consistent with your advice.
Torque is supposedly able to reset the trouble codes, so I'll try after work and to reset it and see if the code returns. How do I locate that particular sensor? Will it actually be embedded into the exhaust pipe right after the cat?

ezone

Acronym for Air Injection Reaction, as some manufacturers call it. "Dilutes" exhaust gases by pumping fresh air into the exhaust system using any of various methods.yes, or in the middle of the cat if it is that design.

HTH

cbjfan2009

Thank you again for the replies. I reset the code when my wife and I got home from work. Big surprise: the light came back on, so I guess I'll have a date with the underside of the car soon.
I'm curious - Alldata mentions testing the resistance of the 4P terminals on the sensor. Not knowing how to do that, I found this useful site with a great description I wanted to share for anyone else looking:
http://troubleshootmyvehicle.com/hon...nostic-tests-1

Do I just penetrate the multimeter probes through the wire's outer sheath? If the sensor turned out to be functional and it's another problem, do I then cover those holes with electrical tape to keep water out?

I'll update when I get under there. As always, thank you very much!

ezone

Yeah, it's like that.

You test at the unplugged connector terminals, if you are going to test at all.

Do you know what values you are looking for when you test?
EDIT: Nevermind, I just now read the article linked above. Their ohm values are correct.
NEVER!
Not when wiring is outside and exposed to the elements.
No. Not. Never.
Tape is not good enough for true sealing of wiring that is exposed to the elements. It will not stand the test of time.
But you aren't going to need it anyway.

cbjfan2009

Here's another update:
I jacked my car up to investigate. I figured out another problem which might need to be taken care of first before the sensor. I've been hearing rattling when I ride with my wife in her car (the Civic), figured it could be the Cat rusting. Sure enough, take a look at these pics I took today. Rattling mystery solved. The wire and "port" coming out of the middle is the O2 sensor, yes? I'm going to borrow a co-worker's floor jack and stands this weekend to get under there and hash some more details out.
Any thoughts on the "safety" or "it needs to be replaced" concerning the Cat?

ezone

Heat shields are rotted apart, that's common too. There is an upper half and a lower half, all available separately from the cat itself.
Most of the time the hardware is also rusted (rust belt here) and is a headache to get apart without damaging the mounting tabs.

You *should* replace the shields (for safety, of course!) but many people are driving around out there without them.

You could hang it back together with coat hanger, bailing wire, or some hose clamps. I see that a lot.

I wonder if that shield has cut into the wires of the sensor and caused the code? Blown the fuse maybe? (Yes, that's the O2 sensor in question.)

cbjfan2009

That's my thought. I plan to get under there this weekend and fart around with it. If the heat shield (I thought that might be what I was looking at) didn't rub through the wires, causing a short, perhaps it just slipped the connector out of place? I'll find out and write back! I'm betting that, since I haven't had any heat/fire issues yet, the top part of the shield might be less important than the bottom. Either way, I won't park in any tall, dry grass with her car anytime soon until I get it fixed.

ezone

You will find the connector still firmly locked together.

It's (P0141) just a common failure of that O2 sensor, I always expect a bad sensor first.


The top half protects your floor and carpet......somewhat. Under normal conditions..

But if there were a "thermal event" of that cat?
Imagine if it were glowing as bright as the sun (bright orange-yellow) under there, how important are those heat shields NOW? (They just became really important now!)
The cat can get that hot if it is fed enough raw fuel (i.e. severe misfire, dead cylinders, mistimed, bad gas, injection failures, etc.).

cbjfan2009

Great news! The heat shield did rip through two of the wires. I purchased a new Denso downstream O2 sensor.

Steps I took (hope this helps some other newbies like me in the future):

The original was in there like a b***h, so I soaked it overnight in liberal amounts of PB Blaster, since I've read it has some of the best penetration/lubrication. Then I sniped the wires and used a standard 7/8" deep socket on my 1/2" socket driver to break it free (the specialty cut-away socket was slipping too much to really wail on it!).



Then I used compressed air to blow away any debris from the cat threads, applied anti-seize to the threads on the new sensor and hand-threaded it. Then I used the cut-away socket to tighten it to a snug fit (I don't own a torque wrench, so I made sure it was pretty tight).

http://postimg.org/image/me7l40qfr/

Last but not least, to fix the rotted cat heat shield vibrating and flopping about, I used large hose clamps to lock it down. Hint to anyone else trying to do this, don't use huge clamps - a couple of 3" size together will probably be better. I had way too much extra as you'll see in the last picture, which I attempted to cut off.

http://postimg.org/image/cuw73xo41/

Tons of thank-you's to Ezone for the insight and advice . I reset the MIL light and it hasn't come back on! I hope this post is helpful to others in the future!