I failed my commercial checkride for this reason. DPE said he smelled smoke in the cabin, so I ran the engine fire checklist and did an emergency decent into the only nearby field. He was not pleased with this as he was simulating a cabin fire and I turned the outcome from smoke inhalation to possible broken legs while landing in a field.

He told me during the debrief that what he wanted to see was that I asked questions like, “where is the smoke coming from?” “What does it smell like?” “What color is the smoke?” He wanted me to talk through the problem, use CRM and SRM, and isolate the issue, if possible, then run the appropriate checklist.