Gents,

Not sure if this belongs in the technical forums - Mods feel free to move if so.

Anyways --- Recently purchased 01-1295 that came with a black works racing test pipe and was naturally throwing upstream and downstream O2 sensor codes. I initially thought it was due to not having a catalytic converter so I installed one and the codes did not clear. Two weeks ago I bit the bullet and bought upstream and downstream OE fit NTK sensors and only the downstream code cleared. I then thought I bought a defective upstream unit and just replaced it with another to no avail.... I am using one of those wifi obd2 readers and clearing the codes via the DashCommand app. Every time I attempt to clear the code it comes back on within 10 seconds. The oxygen sensor lead wire colors DO NOT match the female/engine side of the harness. It does plug right in and fits snugly it seems.

I could not find my multi-meter to read voltage and resistance on the female/main side of the harness but I couldn't find any nicks/cuts/melting etc. Is there a fuse for the heater leads somewhere? Any suggestions??

Pics for the hell of it...

 

I had this happen with NGK oxygen sensors I bought from the auto parts shop. Went to Acura and bought one from them and it worked right away. I think its the o2 sensor issue and the ecu is sensitive to particular models.

 

Quick update --- The harness side is definitely seeing voltage but the diagnostic app I am using shows that the bank 1 upstream sensor voltage is pegged and not fluctuating as it should. Does this sound like a ground problem to any of you?

 

That was the exact problem I had with a NGK aftermarket o2 sensor I got from a generic autoparts store. Maybe find a denso one or the oem Honda and I bet it will work again.

 

UGHH! This will be the 3rd attempt with a new sensor... I did find some sketchy wiring at the ecu harness (soldering and electrical tape).... just trying to verify which wires are for the upstream sensor and ensure continuity etc.

I'll post pics when I get home...

 

The entire 2 years I owned the car if had this problem and I've did everything you have with the same end result ... I had a new aftermarket cat on the car when I bought it . That was taken off and replaced soon after I bought it. Try buying the oem new o2s as I've been told that will fix the problem but they are quite pricy .. IMO you should buy those and if the problem persists then keep trouble shooting

 

Ok so I finally found out that the service manual P0135 troubleshooting does not line up with the ITR ecu harness at all. I gave it up for the night but I will have some soldering and shrink wrapping to do once I get the testing done on the correct pins. Hopefully the continuity tests on the correct pins for the primary O2 sensor will pass and there isn't a short between the harness and the O2 sensor. If this is the case then I will bite the bullet and order a new sensor from Chase.

Here are some pics and the mess I need to clean up. I think as bad as it looks the wiring is still functioning properly but who knows. The car was throwing no other codes and everything has been functioning just fine.

O2 voltages while running --- Note the primary voltage stayed pegged and didn't move from 1.27v :

 

have you done an actual hard reset on your computer? No just flash reset?

Disconnect your battery
Remove plugs from ECU
turn car to acc to drain out power for a few seconds
let car sit for 15 mins
reconnect ECU
reconnect battery

check for codes

 

I didn't know there was a hard reset procedure. I will definitely give this a go later this week.

Thanks!

 

I found signs all over the car that in a a previous life it had a good deal of mods so I don't doubt it had a vafc... However I never had that mess on it I was also told to swap ecus and see if that fixed it

 

Thanks John... I've noticed a few things too.... Missing header bracket, Mfactory trans drain bolt to name a couple...

Nothing that really bothers me but just trying to iron out the small stuff.

 

The header bracket I did not put back on as I was in a hurry when putting the factory exhaust on before driving it to ryan... He has it in a box that I gave him. Also the mfactory oil drain and trans drain I installed. The car actually still has my mugen oil pan that i didn't have time to remove but I guess that's yours now oh well

 

I know for certain there is not an Mfactory drain bolt on the oil pan.... I am wondering if it was swapped out but will drop the pan on my next oil change to find out.

You have been the only previous owner I have been able to get in touch with. Ryan and the owner before you haven't responded to any of my messages. I don't care about the previous history - what's done is done and I just want a few answers to resolve the minor issues with some intelligence and get heR back to where she should be. I'm talking like there is a bunch of problems... LOL! I'm just being real obsessive compulsive with heR...

 

Quick update... I found the correct pinout diagram for the R harness and did some more trouble shooting... checking for continuity etc. Everything seems to point to a bad ECM... The car runs great otherwise so I'm not sure how common it is to have 1 circuit go bad on an ECM.

If anyone in the Northeast near Philly/SouthJersey has a spare P73obd2 ecu please hit me up!! Or if you want to bring your R out and meetup I'll pay for your gas and lunch!!

One other thought --- I have a P72 obd2 ecu... could I test with that?

 

Yes you can. It would run a little different under WOT and up top in rpm range bc of different fuel mapping from GSr to ITR.

But you wont be doing any of that

Just swap them out and start the car and let it idle for a bit to see if light comes on. If anything, go for a easy drive around the block. Its not going to hurt anything if you do. Just dont leave it live that or go beating on it. (That wont really do anything either, just not the right A/F ratios and mapping for that motor)

Good Luck

 

Forgot to follow-up with this again but I did swap out my P72 ecu from my '01 GSR and the ITR would not start with it.... Is there maybe some security feature I'm not aware of?

Thanks for the help and input on this guys.

 

^^^ Yes 00-01 cars have an immobilizer. The ecu has to match the key.

 

99-00 civic si ecu would work

 

I have been having a very similar situation to what you have been dealing with, did you ever find out what the cause was?

 

Earlier this year I made a full video on this on YouTube. My po135 kept coming back. I finally ditched all auto parts o2's and got a nice Denso online, and all is great. I kept burning up Bosch O2 sensors wasting money. Denso is Asian and works perfect Bosch is German and didn't do good. I should have known that

 

Even a new OEM sensor didn't fix things for me. I started to think I had a wiring issue but finally tried a different ECU which cleared it up.

 

Resetting the ecu clears the code, but it also clears your DTC's. You'll need to drive it around to get them ready, I believe once you have them ready you'll know if you still have an o2 sensor issue.