I have a Goodman GMNT080-4 (90%). I'm having the same problem
As Streatherg did back in the Nov 2006 question. I reviewed his article and tried
Every thing on there but seems to be doing the same thing.
The furnace kicks on for about an hour then locks out and has to be manually reset threw the thermostat or the power switch. The led light blinks 1 time and it says it could be
1. flame sensor 2. gas pressure 3. gas valve . I cleaned the flame sensor , checked the gas pressure but don't understand why the gas valve would fail if it runs fine for a while when first starting.

If you have read the code right, this is one of those things that drive service men nuts. A part is probably failing, you will have to be observing the problem as it happens, or more likely the problem will worsen and present itself.

This problem has been going on since the beginning of the season, and I've had service
Guys just come clean the flame sense and check gas pressure, but they tell me the gas valve seems to be doing it's job. Would you recommend me getting gas valve changed? Or
Do you think it might be something else like the circuit board? I was curious if you ever heard back from Streatherg from the Nov question? I'm having the same problem as him and just wondering if he ever got his operating normal? Thanks in advance!

The gas valve could overheat/defective. You can test to see if it is the problem by taking a meter ad place the leads on the valve. When the valve is operating normally you will have 24 volts to the valve. If the valve drops out with the power still applied then you know it is the valve. If the power drops to the valve causing the furnace to shut down then you know it is not the valve. We use electric recorders/event recorders to check this out. It beats standing at the furnace waiting for it to fail. One of the first things I teach my students is how to save time and the event recorder does that very well. I

Thanks, I'm going to check that as it fails to see if I can catch 24v at gas valve before it
Goes in to lock out mode. I appreciate all the help! Thanks again.

The problem is the stack over temp sensor located on the front of the fume exaust fan. The stack over temp sensor is prematurely tripping thus dropping the 24v to gas valve. The unit tries to re-light 3 times and after 3 failed attemps the circuit board goes into fault mode with the flash code of 1. This is the code for ignition falure. When this occurs the power to the furnace must be cycled to return to service. You can test if the stack sensor is bad by bypassing it. If the furnace runs normally then you know it's the stack over temp sensor. P/N B1370254 for the GMNT080-4.