just ask that dumb @$$ at suzuki what mechanic have done is exactly the same which a car may observe in routine operation that a wire to fuel pump got broken due to any reason and its disconnects from FF wiring, does only this blows suzuki ECU????? absolutly nonsence. whenever a sensor or any thing connected to ECU goes off the circuit you will have check engine light.
i changed engine of my city with identical one so i didnt changed the ECU, but at that time a kabuli ECU for my city was costing 45k from chah sultan, thats the asking price for city 2k model