I'm helping a friend, he had his 99 Jeep Grand Cherokee 4.7L 4WD sitting in his yard for about a year with a bad engine... The engine must have overheated bad because both head gaskets were shot... I told him I'd replace the engine for him. Well I just finished bolting the engine up to the transmission and I hooked up the grounds and the important stuff, like crank & cam sensor, oil pressure, tps, iac, map, ect, iat, the electric fan, alternator and it turns over but it will not start. I checked to see if the COP coils were getting signals from the PCM, the coils are getting the primary feed about 9v but the PCM is not sending the switching signal. I swapped the crank sensor, no difference. Also my Launch crp123 scan tool will not power up when I connect it to the DLC. Any Ideas??? lol this is my first swap in a Chrysler product.

 

uh, well, yeah. So you replaced an engine and are asking us why it doesn't start. We need a little more info. Such as, did you replace it with another same year same engine 4.7...did the new engine run before you swapped it....is 9v the expected voltage on the coils....which pcm did you use.....
I do believe if the scan tool will not power up that is not a good sign for the pcm, if it is the right one for the car...