My company had a call on this unit, Carrier Mod.48gs-042090301 ser. 4998g10252.
First call: Dia. code was cumbustion failure. Second call: Dia. code was roll out failure.
Third call: Carbon Monxide det. was going off in res.
Replaced heat xchanger. When you cycle unit inducer starts,spark igniter sparks, gas valve opens,we have ignition. Flame only lasts for five to ten seconds, goes out retries, relites and goes out in 5 to 10 seconds. It will do this 3 or 4 times and some times it will light and run normal but not until it has warmed up. If you shut it down and let it cycle then restart it while it is still warm it will lite and run normal. Sometimes it will spark when the burners have been going.
Things i changed per Carrier Tech. support.
Flame Sensor, All burners, Burner bracket, Gas valve, all ground wires, control board, Hall switch and heat exchanger. Somebody throw me a bone.