I am wondering if my Oxy sensors (front-left and right) are a bit slow to warm up, requiring cleaning or new sensors.
On cold start (open loop) everything is normal, but after about half mile or so, when the motor is now in open loop, I get "171" and "174" (abbreviated) codes. I have a ScanGauge and can erase/reset the codes en route.
Thereafter on each trip there are no further check engine light warnings.
My first thought was an exhaust leak that closes up under heat expansion. Exhaust connections seem tight.
I also checked intake tract and everything seems nice and tight.
Thanks for your comments, ideas, etc.
My Jaguar is an '07 XK with 32K miles - lots of short trips, which can carbon exhaust.

 

Stop clearing codes. Follow the very frequently posted advice (use Search). Use the full code names.

 

If your O2 sensors were the problem, the system couldn't determine a lean condition. You have something else going on. Either an air leak, lower than normal fuel pressure or a Mass Air Flow sensor error.

Good luck!