NTI ER6 code in cold weather

I put this problem out there last year and thought i had it fixed. I was wrong, or should i say my gas company was wrong. I keep getting an error code ER6 on my trinity 150 propane boiler when temps drop down around 0. If u by pass my exhaust senser, it will run with no problem. My circulator is on high moving water through the boiler as fast as possible, the boiler is super clean, exhaust test were exellent, gas pressure is 11 lbs. my boiler high is set at 180. After error code, you can turn power off then on and it will run for 1 cycle then i get error code ER6.

Any info will help thanks. Panman