when first started from cold 02 wrx wagon makes buzzing noise then stops after about 1 min of engine running from cold, as engine warms up and is restarted buzzing noise is on for less time, and when car is started from hot no buzzing noise,been told ecu ans expensive fix ,any thoughts please

 

its like a clicking,plasticy hollow sounding buzz

 

could be a relay (the subaru has lots !) - try narrowing down where the noise is coming from - the ECU is in the passenger footwell