Is there a DIY way to test if an EEC IV computer is defective? All the parts stores around here have gotten rid of their PCM testing equipment. I have a 2002 Sport Trac with a 1998 Mountaineer 5.0 drivetrain. It suddenly quit running while at idle. I changed the crank sensor and it would run but very horribly. I'd put the original PCM from the Mountaineer in, to no effect, before changing the crank sensor. Then I put the PCM in which I'd bought online, programmed with the VIN and latest software. That is the one installed when it died. No spark. So I reinstalled the other one, again no spark - after it had just been running with that PCM. Of course I disconnected the battery when swapping PCMs!