Ok, I recently got a SES light with an indication of a P1273 which is translates to "Air/Fuel Ratio Sensor 1"

I got this about 1500 miles or so after I put on my ypipe back exhaust. I've had jwt popcharger/plenum/hf cats/ypipe for over 10k miles and never had this check engine code.

Now what the heck is this exactly? I looked at the list and there were like 5 other codes with this exact Air/Fuel Ratio Sensor 1 indication.

Is this the MAF? The O2 Sensor?? Dirty air filter?

Please help me out here, Thanks!

 

Does anyone know if this is at least a minimal risk code?

Where should I be looking to solve the problem?

 

I have the same code... as well as P1283. I believe it is from the O2 sensors(as I just installed test pipes) and have also had them in the past. But I have also heard of a TSB(Technical Service Bulletin) from Nissan, which given your mods is probably the case with your Z. As it is now, I've got the spark plug non-foulers installed and plan to give my car about another 2 weeks before I decide to take it in for the TSB. I have a OBD II Scanner, so it isn't that big of a deal to me, mostly just an annoyance.

 

1273 is lean on driver side O2 sensor. I think the 1283 is rich on one of the O2's.
I had a 1273 last week that I think was a product of an exhaust leak above the cat. I reset the ECU 3 or 4 times and it finaly didn't come back, which means my ecu probably adjusted and started dumping fuel to it.

 

Hmmm...I'm going to just have to pull off both my cats and send them back for a new pair. I recently had a shop repair a cracked weld that went all the way around below the cat on the passenger side. I reset my ECU but the code still came back. Seeing my driver side cat from the bottom didn't show any signs of leakage, but as you guys have indicated, it's probably more than likely a leak on the driver's side as well. Damn these cats, so much trouble.

 

just for reference P1273 is not related to the down stream sensor. it is a lean condition seen by the upstream sensor. If you guys throw on testpipes and get a P0420 or P0430 that is something that can be taken care of with the HELP! nonfoulers

 

Thanks! I always thought that the P1273 and P1283 codes were from the lean condition and thus not from test pipes... it just never made sense as to why that would be causing it, I guess it was just some sort of coincidence that I got them after the test pipe install both times... or perhaps the test pipes can in some way be related. Hhhmmm, maybe the rear sensors are telling the ECU that it is running slightly rich(from the unburnt fuel, but not enough to throw a P0420 pr P0430) and it is leaning out the mixture. I'll take it by my local Nissan dealership soon and have them run the TSB procedure on it and keep you guys updated. Thanks again Zivman

 

It is more than a coincidence. When you free up exhaust flow like you did with test pipes/HFCs that can lean out the AFRs. the ECU should adjust overtime, but not in every case. The rear sensors are nothing more than dumby sensors telling the ECU if the cats are working. The upstream sensors have a much more critical role and you want to make sure they are working correctly.

 

Yeah, 1273/1283's come from the O2 sensor in the header just before the test pipe, but if there is a large enough leak it could throw a lean code. Well, that's what I'm hoping anyway.
I should have my exhaust fixed and Utech running this weekend. I don't think the ECU adjusts immediately, so I should get a very rich a/f log right after fixing the leak. Thats my running hypothesis anyway.