How can you tell if you have a bad ECM? I have a 93 TA and the problem i,m having only happens when the car is up normal running temp. When it is cold the car runs perfect. When it gets up to tempature the check engine light comes on and fans comes on speedo stops working and car won't rev past 3000 rpms starts cutting out. When the check engine light is on it will not allow a scanner to read it. It says connot connect or check plug to scanner. When it is cold it will read it but no codes show up. Anyone know whats wrong?

 

Check your ECM plugs. They may be loose or dirty.

 

Bad grounds will reak havoc. I had an issue where when at temp my grounds would not be as good, I pulled them off, cleaned them, and it stopped temp related issues.