....I have a P0138 code showing up. I have a res delete and an aftermarket CAT so I purchased an O2 delete from ZZ Power (to remove the subsequent P0420 I was getting) which has worked great until now. My fuel pump failed a couple weeks ago and I had it replaced and now I'm getting a P0138 could the fuel pump failing have messed up my O2 delete some how? Or is it just coincidence? Or maybe that code throws when the fuel pump fails? Any suggestions?

 

The_Maniac knows a lot about codes and all that.
Hopefully he can help you once he comes on and sees your post.
If he doesn't post a response in a day or so, I would send him a PM and see if he can get you pointed in the right direction.

 

Thank you I'll do that....

 

Oxygen sensor bank1 sensor2. If your secondary O2 code was removed, it wouldn't throw it. That's possibly a primary O2 sensor failing. If you have a scanner, check the oxygen sensor values. At idle it should bounce all around from like 100 to 800. If it stays at a single number too long, that's a problem. Could have just thrown the code from idling too long on a hot day. Clear the code and see if it returns.

 

Thanks I have a scan tool but its a very basic one that only reads and clears codes it can't capture live data. I don't know how long the code was actually there but I THINK it only showed up after the fuel pump issue. I say I don't know how long 'cause I got a stupid EGR code showing up all the time. I cleared all the codes and I'm gonna see which ones come back.

 

So I'm still getting this P0138 code. One thing I have noticed is when this code is present and not cleared I will get a rough idle or "loping" at a stop light which is about 30 seconds from my apartment....this occurs right after startup generally. The rough idle doesn't last long its about 5 seconds of rough idle only. If I clear the code I don't seem to have any rough idle or issues.

I have the rear O2 deleted with a ZZ Power O2 delete. Is it possible that its something like the crankshaft sensor: Chevrolet Monte Carlo P0138 Engine Trouble Code - Chevrolet Monte Carlo P0138 OBD-II Diagnostic Powertrain (P) Trouble Code For Chevrolet Monte Carlo | EngineTroubleCode.com
This sounds like what I'm experiencing, or is it possible that its the front O2 sensor? I would think that front one would throw the proper code? I have had that front go bad in the past and I had the proper code and no rough idle.

Any suggestions if anyone has had a bad crankshaft sensor throw P0138?

 

Eh, just looks like an O2 issue... sensor 2 though is behind the cat, so maybe that thing from ZZP isn't working right or the code just remains, and your rough idle may be unrelated. Try unplugging the MAF sensor before you start it and let it idle, see if anything changes.

 

So unplug the MAF sensor.....let it idle....then plug in the MAF and drive and see if I get the rough idle?

 

I would say first just start the car and let it idle, see if it hiccups, or put it in D and hold the brake to see if it happens. If so, then unplug the MAF and try again.

 

Well I didn't get a chance to do that and now the code has come back and is gone again? I had a pretty long drive over Christmas like 2 hours and all was good. I drove another short distance when I got to my destination and back again....the light came on on the return trip. I got up the next morning to drive a short distance again....and the light was out and has stayed out now all the way back on my 2 hour drive? If it was an O2 (front or back) wouldn't the light come on and stay on? Those don't give intermittent problems do they? I thought once they stopped working they were done?