How do you test a ecm on 1990 Chevy 5.7?

Answer 1

the only way that it can be tested is if you take it to a mechanic shop and they hook it up to a computer... if its not working right you can reset the ECM unit by taking the negative and the positive battery cables off the battery and hold the cables together for 10 to 15 seconds and this will reset the entire ecm.... done this plenty of times on different trucks... learned it from a buddy of mine that i worked with at a mechanic shop