Originally Posted by greystreak92

Hold the phone guys, the computer won't make "heavy metal knocking sounds from below" or even cause the engine to do this. So just throw that idea out the window. the computer controls fuel/air ratio, ignition timing and emissions equipment. The 5.8 doesn't even HAVE a knock sensor. Furthermore, the Codes don't do anything but provide diagnostic information. If the computer gets enough incorrect or "unexpected" information from the sensors it will automatically go into "limp mode which PREVENTS the system from damaging the engine.

To be honest, telling you that they needed to replace the computer without first telling you exactly what they DID get from it is pretty far fetched. There are Codes for everything up to and including a hard fault memory failure (think of it as a hard drive crashing) or a loss of reference voltage. The ONLY possible scenario I can think of that would leave the computer inoperable and unable to get ANY information from it would be an electrical failure that would render it completely dead. In THIS case the engine wouldn't even turn over. And it takes about 20-30 minutes to run BOTH a KOEO and a KOER test and that INCLUDES the warm up time on the engine! Neither test requires taking ANYTHING apart. 3 hours of diagnostics? Seriously? And THAT when the engine was still running? Sorry but that is beyond "fishy". If the truck runs great now, get under the hood and have a look at exactly what parts appear new. If nothing has been touched, or appears new, and they did replace the computer without troubleshooting anything else, I'll bet dollars to doughnuts that you will have the same issue or worse within the month.