I have a 91 z28 305 tpi and the cooling fan(driver side) is always on. So I pulled the ecm out (still connected to car)and gave it a jiggle and what do you know the fan went off when just the key was on (engine was never started) then I wiggle it again and the fan goes on. I can wiggle the ecm all day and the cooling fan will kick on and off like this . My question is this a wiring issue or do I need a new ecm??? There is a replacement ecm in the car now the po must have installed.how can I check that the ecm is grounded? Anyone else had this problem? Thanks in advance

 

Most likely the ECM is bad. The pin on the ECM connector for the primary fan is E8. That will be the yellow connector.

RBob.