Timer won't advance in Auto Mode

Hi,
My GE dryer works OK in timed mode, but the timer doesn’t advance in auto mode, so the dryer keeps on running until I open the door. The heating appears to be working OK. My understanding so far is that I need a) check the resistor to make sure it reads 20 Ohms and then b) check heating coils (not sure how to check these). I haven’t been able to find the resistor in the diagrams http://www.appliancepartspros.com/parts-for-ge-dpr483ga0ww.html, though, so not sure if this model has it or not.

Can you guys please tell me what my troubleshooting process should be? Let me know if you need any other info.

Thank you,
Dee.