Issue with Bryant Furnace code 34

zepfan

We are having an issue with a Bryant 90% furnace
Model# 340aav060100absa. Serial# 4707a03943
The issue is the unit is locking out on code #34, ignition proving flame fault. We have done a full combustion test on the furnace, all readings were good. We cleaned the flame sensor, checked the burner offices, found the inlet gas pressure to be 5”, the manifold is right at 3.5” , and checked the burners to make sure the carryover portions were open and not rusted, or blocked. The igniter is 55 ohms at room temperature, and we also tested the furnace for proper grounding. We have cycled the furnace several times, and it comes on and heats every time. We have been to the job twice and are yet to catch the furnace not being able to establish flame. We replaced the gas valve today, and hope that was the issue. Has anyone else had this same code with this particular Bryant/Carrier furnace? If so what was the resolution? Thanks to all