We have a G40UH(X) by Lennox which is about 5 years old. The pilot light on our lennox G40UH(x) series furnace won't light. The blower turns on for a few minutes but blows cold air and the pilot light never comes on. The LED #1 light is off and the LED #2 light is slow flash. May I know how can I fix this?

Manual see page 18 figure 4

http://0190acd.netsolhost.com/manuals/G40UH_Series.pdf