Will Diagnostic Check find a faulty relay

[GGGti75]

I know this may be a siilly question, but here goes.... Will a diagnostic check find a faulty relay? i've just found out my mechanic didn't use his diagnostic equipment after carrying out the repairs that were needing done, once he had done them there is a problem with the car running now after about 2/3 miles it just chucks it. After asking for some advice i was told it could be ECU or fuel relay.

 Thanks in advance

[axewielder]

no diag doesnt find faulty relays, they are a pretty cheap+ easy first try though

[Cable]

it will pick up a problem ie. open circuit, but it wont tell you that its a relay

[axewielder]

rly? all i heard was that it didnt on the mk3? ne way good luck finding the fault, ive been there+ so have lots of us 

[GuessWho]

it will pick up a problem ie. open circuit, but it wont tell you that its a relay

Yup.

Snap On tool I use at work just displays "Open circuit" then gives an error code to what circuit it is.

[GGGti75]

Nice 1 guys. Hopefuly gettin it checked out today, i'l let you know how it goes