Help diagnose check engine light Code P2272


jcthorne

GT Owner
Aug 30, 2011
792
Houston
I got a check engine light last week. Hooked up the X3 and pulled the code P2272. Only code stored. OK, that is driver side downstream O2 sensor stuck lean. Checked for any obvious wiring or hose issues and found none so bought a new Bosch O2 sensor and installed it. Cleared the code and all seemed well for a few days. Today the CE light is back and same code....

It may have never really gone away just took a few drive cycles to come back.

Any suggestions on diagnosing this? I am running one of Torrie's tunes but as far as I know the secondary O2 sensors are not turned off. I also have an Accufab exhaust but the stock cats are in place.

Any suggestions or experience would be appreciated.

Thanks.
 

AMB

GT Owner
Aug 29, 2005
401
San Diego,Ca.
You may have a BAD cat!!! Do you have any upgrades??? How much boost are you running??
 

jcthorne

GT Owner
Aug 30, 2011
792
Houston
Guess it could be. But would have figured the secondary O2 would be stuck rich if this were the case. Perhaps not.

Suggestions on how to diagnose? I am not going to just start replacing parts as that gets expensive quick. The o2 sensor was cheap and easy to install and a normal wear part anyway.

I have a pulley and tune, approx 15 psi from stock blower according to the dash gauge. Stock throttle body. Accufab Exhaust.
 

tmcphail

GT Owner/Vendor
Mark IV Lifetime
Apr 24, 2006
4,045
St Augustine, Florida
I can terminate that side of the calibration and that will end the code.

Since you replaced the sensor there are only 2 other areas that could be at fault. The cat itself being bad or the wiring between the sensor and the PCM.
 

jcthorne

GT Owner
Aug 30, 2011
792
Houston
My experience in the past with tunes that turn off the secondary o2 sensors is that they will not pass emissions testing as the processor will not report a ready condition. Is this true in the GT? I know it has the older style processor like the 04 Cobras.

Torrie or anyone,

Can the X3 be used to display values for the secondary oxygen sensor while driving to aid with diagnosis? If its a wiring fault, the value will likely be 'stuck' where if its a cat going bad, will likely show some real readings, just not what the processor is looking for.

For wiring fault, I suppose I should get a pin out of the connector and check for power and ground for the heater circuit first. Will dig out the troubleshooting diagrams from Ford and try that.

I'd rather go catless than spend $$ for new cats. Accufab exhaust with cat eliminator pipes gets pretty loud I've heard.....

I need to nail down what is really going on before I make decisions. Appreciate the help!
 

tmcphail

GT Owner/Vendor
Mark IV Lifetime
Apr 24, 2006
4,045
St Augustine, Florida
That depends on the stringency of your testing. But there are other things I can do as well. You should be able to log those functions with a laptop and livelink
 

jcthorne

GT Owner
Aug 30, 2011
792
Houston
Ours pretty much only requires the processor to report OBDII ready and no current MIL codes.

I'll load up livelink and try using it this weekend to get a diagnosis for what is going on. Once I know, will discuss what makes sense for the car.
 

tmcphail

GT Owner/Vendor
Mark IV Lifetime
Apr 24, 2006
4,045
St Augustine, Florida
Sounds good.