My tromm dle 7177 is blowing cold air and the check filter light stays on

There is a upper limit and lower limit thermostat I believe, YouTube repair clinic channel has all the test info and parts.
https://www.youtube.com/user/RepairClinic

sensor bars just measure humidity so dryer knows when close are dry, so will have no effect on heating. the check filter light is just a reminder, not connecter to any sensor or anything. could be several issues: gas valve solenoids, thermal fuses, etc. but for a quick try that might work, try just unplugging the dryer, push and hold the on button for about 20 seconds and then plug back in and see if the dryer is reset. works sometimes. good luck

check for air flow in the vent make sure the vent is clean and no kinks in it

check the filter could be stopped up

Check the 220 volt circuit breaker or cycle it. If on the other hand you have fuses instead of breaker panel, with 220 volt you should have two fuses to contend with and one or both may be blown.

Unplug it and wait a minute, then plug back in. This is my first line of defense, then all I know, is I won't buy another LG for my home. No one wants to work on them or they don't know how. I own 4 LGs in my home, 2 have had issues....grrrr.

What happens on timed dry?

Check the vent pipe behind the washer for clogs or kinks also check the outside termination for clogs

Clean the vent all the way to the outside.
The dryer will take 4-5 loads to reset the filter sensor.

Mahe sure the vent is not smashed behind the dryer.

Check for a blown thermal fuse or a faulty heating element. Both components can be tested using a multimeter or ohmmeter. Check for continuity. A lack of continuity indicates a faulty component. The thermal fuse is about an inch long and is located just inside the rear of the dryer and is usually attached to or near the exhaust duct. Hope this helped and best wishes.