Its comes on for about 15 seconds and then cuts off

I assume you've already addressed this (I just came aboard), but here is what I would've told you:

There is a component test built into this furnace that might help diagnose the problem.
If you're handy, it is a simple procedure (if not, get someone who is!).

There may be instructions for this on the furnace cover, but the basic procedure is:
1. Shut OFF the room thermostat or disconnect the "R" thermostat lead.
2. Briefly short the TEST terminal to the "Com 24V" terminal.

Status LED will flash code and then turn ON the inducer motor.
The inducer motor will run for the entire component test.
The hot surface ignitor, blower motor-heat speed, and blower motor-cool speed will be turned ON for 10-15 seconds each.
Gas Valve and Humidifier will not be turned on.

You should be able to see/hear each component work (or not!)

Best of luck,
Wally H.