Hello,

Recently my SES light came on and is showing code P1273, Air/Fuel sensor 1 running lean. From what I understand, this can be due to a couple of things:

1) intake leak
2) dirty/faulty MAF sensor
3) exhaust leak at headers
4) faulty O2 sensor (pre-cat).

Previous to the light coming on, I started hearing a loud ticking sound when I open the throttle up a bit. I'm not sure if this is knocking, an intake/exhaust leak, or what.

Any ideas?

 

Fixed it, plenum bolts had become loose since installing the Motordyne spacer a few months ago... SES light went off and hasn't come back on. I'll be taking them all out and applying loctite this weekend. Anyone use RTV to ensure a good seal here?

 

I had the same problem and it was a loos hose.

Here is a good information about the P1273 code: http://engine-codes.com/p1273_infiniti.html

 

Don't use RTV. It's too messy and not necessary.

 

Which hose was loose? I have this code.

 

Bump for which hose

 

FIX for the code P1273 on my 04 G35X:. After months of trying to fix the code that just kept reoccuring. I checked for leaks, replaced the O2 Sensors, checked Fuel system pressure, reset the ECU, etc.... I just couldn't figure out what else it could be.. What else could be causing the lean mixture.. I decided to replace the Spark Plugs and THAT WAS IT!!! Its been 2 weeks and I still don't have the code back. Apparently, one of the plugs was not working right and/or fouled and causing the lean condition. I'm so happy I have to tell the world. That was my last attempt before I got robbed at the dealer service.

 

+1 on the plugs, I changed all 4 O2 sensors, fixed an intake leak, then removed the CAI and put back the stock intake back on. Light still came back on, sea foamed the fuel system, the car has 102,000 miles so I changed the plugs, which were absolutely spent even thought the car ran smooth .A couple plugs were even loose but no CEL anymore since the plug change.