Following Honeywells guide
http://customer.honeywell.com/techlit/pdf/69-0000s/69-1383.pdf this occurs after the inducer is energized which never happens so I am confused where to look next. The Pressure Switch isn't that expensive but I don't think it is bad and I replaced the inducer already because last year the motor made some noises when starting that made me think it was on the way out so I jumped the gun on replacing it already..
3 Flashes
Pressure switch circuit was still sensed as
open 30 seconds after the inducer was
energized. System is in 5-minute delay
mode, with inducer off. After 5-minute delay,
new ignition sequence is initiated.
NOTE: SmartValve On/Off switch in OFF
position during a call for heat generates this
flash code.
1. Move SmartValve control switch to ON>
Valve is on
2. Inducer and inducer wiring.
Already replace
3. Low line voltage power supply.
4. Airflow proving switch operation, tubing, wiring.
5. Obstructions or restrictions in appliance air intake or
exhaust flue system that prevent proper combustion air
flow.
6. Other devices (such as auxiliary limits) in the airflow
proving switch circuit.