Hyundai Repair: checking relays/ECM, engine cranks, test apparatus

Question
is there anyway to test a relay or the ECM to see if it is good

Answer
A typical relay has a coil side and a contact side.  When voltage is applied across the two coil terminals, there should be continuity across the contact terminals.  Many relays now have a diagram drawn on the relay itself.  To test, you'll need to set up a test apparatus to apply the voltage and use a meter to check continuity.

As for the ECM, how readily it can be tested depends on the suspected malfunction.  For example, if you suspect the ECM is not turning on (engine cranks but will not start and no check engine lamp illuminates), then you'd need to check for proper power and ground to the ECM at all the specified terminals (using a schematic).  If proper power and ground are in place and the ECM does not turn on, then it's safe to conclude the ECM is defective.

In general, actual ECM testing is not possible.  Conclusions are made based on things the ECM should do (such as illuminate the check engine lamp and provide a 5V reference signal for certain sensors) and inputs to the ECM.  The idea is to use a process of elimination to verify every other potential cause has been eliminated.