[SOLVED] CEL after downpipe install ( P0134 )

installed a new cat less downpipe. reused the oem o2 sensors, got p0134 immediately, AFRs stuck at 14.8. inspected wiring and found no pinched wiring. checked connector and found a spread terminal on the black connector on the female side. fixed it, but still getting 14.8 for AFRs and no change after warm up, as far as I can tell o2 sensor is good. connectors are good. checked bar fuses and both are good. disconnected battery for 30 min. still no change. I've got a new OEM o2 sensor coming, but is there anything else I should look at or test? any help is much appreciated.

 

When you say stuck at 14.8, you mean not even changing a little, even if you rev the engine?

You have to be careful with spread terminals, what was the damage and how did you fix it? To what degree? In other words, are you confident the contacts are making a good connection now?

 

One terminal was a little spread out, I Depinned it, squared it up and put it back. I do this atleast once every few days at work so I'm fairly confident in my repair. Also, back probed and verified continuity across the connector. The AFRs do not move. At all. Not when driving, revving, cold, hot, nothing. The dtc is for that upstream o2. However even after the repair still have the same results. I fear the o2 is damaged internally or something. Got a New one on the way so well see if it fixes it I guess.

 

Your credentials check out haha, How did you back probe the insulated connectors?

For a DP install, you would have had to remove the sensor, how much trouble was it removing it for you? Did you have to apply external heat?

 

I used a pinch and essentially made a small puncture in the insulation around the wire on each side of the connector. Used a touch of liquid tape to patch the spots when I was done. They were kinda a bitch to get out. After I unplugged them I let them soak for about an hour in penetrant. Still sucked to take out. Threads were trash. Chased em alittle and they threaded into the downpipe with a little effort. But no heat used on them.

 

Alright, It sounds to me like we would be picking at straws diagnosing the root cause of the sensor failure, with an irrelevant conclusion. It sounds to me like you are doing the right move by replacing the sensor.

 

Thanks! I'll update as soon as the new sensor goes in. It got delivered to the shop today so hopefully tomorrow after work it'll be in and all my worries will be over lol

 

UPDATE: installing the new NTK o2 sensor worked perfectly. found out the issue with the oem one i removed was that when i removed it, the o2 sensor twisted and broke the ceramic inside. now my afrs are changing like they should. so i guess the tip here is buy another o2 sensor and leave the ones in the stock down pipe.

 

I am happy to hear you found your problem and it didn't cost much! You did your due diligence with diagnosing as well, thumbs up for that.

Thanks for reporting your results with detailed information on what you thought broke, I hope that helps someone diagnose similar concerns in the future.

As a reflection point, these sensors tend to seize into the pipes. If you manage to pull them out cold, there may be immense pressures on the sensor materials. I ALWAYS recommend using heat to aid in removing stubborn components like this - I am lucky enough to have access to an oxy-acetylene torch which I use exclusively. Theoretically, you can even warm up the car up to temperatures to allow the metal to expand, but it may not ease removal enough to get the stubborn sensor out.

 

heat would have helped for sure. honestly I should have just left them in the stock dp and just installed new ones in the catless dp. but hindsight is always 20/20 lol. To anyone doing a new dp, just save yourself the headache and get new NTK sensors. this way you have two sets. thanks for sticking with the thread!