Hey folks,

today, my GS threw these codes. I had troubles with the P0172 a while back, but replaced the pre-cat O2 sensors with Denso units, which seemed to fix it for a while. Now, I'm not sure what to think. Any pointers would be much appreciated!

 

Because they are circuit faults, your problem is either the o2 sensors themselves, the wiring to/from, a fuse or relay, or the vehicles computer itself...