Blower keeps running but burners shut off during call for heat

[mir]

Blower fan keeps running but burners shut off during heat call between 3-4 mints of initial start up.
Replaced the filter which was fully blocked but problem is consistent. Any suggestion

[Admin]

Do you see a LED light, on the furnace control board,  flashing a code?  Have you tried cleaning the flame sensor?

[mir]

Yes i have cleaned flame sensor. Burner come on for 4 mint when first start and than blower fan keeps running, thermostat in on auto. Can this be faulty limit switch?
Furnace model: c9mpd075f12c2
LED Code: 3 blinks

[Admin]

It's a low pressure switch lockout code, according to the ICP C9MPD manual.

Check that your venting is clear and sloped properly, and check the P-trap and drain line are clear.

If those things checkout use a multi meter and manometer to verify if you might have a faulty control board or pressure switch.