Yesterday I did part 1 of a diagnoses test, part 2 will be tomorrow. My bug was in a GE single wall oven. The complaint was the display is flashing "Locked" but the oven wont go into clean mode.
First I tried the onboard diagnostics and didnt get a code, I tried the production test mode to see if the door would lock when I told it to. Nothing.
I pulled out my trusty Fluke 116 and the wiring diagram for the lock assembly, tested and found a bad switch in the lock assembly. My time to find and diagnose the problem was about 10 minutes, of course it helped I had spent all day before the test simulating faults to see what happened and what codes get thrown to test myself, and this was one I tested myself on and when I did it, I didnt get a fault code either, even though the tech sheet gives a specific code for a latch problem.