There is a fairly new procedure for an engine 150 hour inspection. It basically tests the PMA output with the ECU power killed. Hook up your computer, bring up Mterm, run the aircraft at 100% (warn pilot that he should go straight to cutoff, do not pass go if something gets sideways with the engine) pull the ECU Circuit breaker and using the Mterm program view the voltage from the PMA. At that point you are powering the engine solely on PMA power. After 45 seconds you will get a fault light, then you reset the circuit breaker, shut down normally and then clear your fault.