Car: Ford Focus Mk II 2010 Diesel TDCI 1.6L
When I push either turn signal, it lights up the appropriate light on the dashboard and flashes the corresponding turn signal VERY briefly -- about a tenth of a second, and then it clicks off. No matter how many times I push the lever, it does exactly the same thing.
The same behavior arises with the hazard lights, but if I do it three or four times, it'll actually start blinking properly. When it fails, either left or right will blink on its own very briefly.
Note that the turn signal switches off in the dashboard too.
As far as I can tell, nothing else is acting up. Heaters, radio, windshield wipers, etc all work as before.
Please, how do I diagnose this bizarre behavior? There are no DTCs.
I should note that this happened shortly after I programmed a new additional key.