Jeep Grand Cherokee '99 4.7 WJ random crank no start

Hi! First of all history of the work i've done and problems:
-July 2019: problem with alternator while i was 100 miles from home, jeep shut down 3 times trying to come back home. Changed alternator.
-July/August 2019: random crank no start (when hot)
-September 2020: changed PCM (from flagship one)
-Summer 2020: fuel pump died, changed with a Bosh (whining from the moment I instlled it) then changed with another one (still whine) and code P0443 and jeep shakes a lot for 10 sec when cold start but then runs fine (Injectors done 2 years ago)
-March 2021: after 8 hours at work the Jeep (cold start) crank but no start, with the classic 3 on-off i don't have any code and neither the "Done" message.

Still have the P0443 code, bought a new purge valve solenoid but doesn' work so I checked alldata (DIY) and found a series of test (i'll attach) and performed them and this leads me to a possible defective PCM.

My tools: Hantek 1008C oscilloscope, Multimeter, elm327 scanner bluetooth, witech micropod2 clone with DRB3 emulator (only works with PCM don't know why because on the dodge works with every module), OBD2 breakout box

What do you guys think? Should i check something else, crank and cam position sensor? Is it possible I had a bad PCM from the start?

Start from scratch and look at what is working before chasing anything else. Gather evidence. During the no-start, use your scope to verify that injector pulse, cam, and crank are present (and that no obvious abnormalities exists within the waveform, such as the signal breaking up). Practice scoping them when the vehicle is running properly, if you don't have experience with scoping those components. Don't know if you have an attentuator to scope ignition, so just pull out an ignition coil to verify that you have spark during no-start. Focus on gathering that info first and let us know or show us the scope patterns.

Thanks Jm for your suggestions, I will practice scoping for sure. I think I can practice on the crank and cam sensor, I have the attenuator to test the injector pulse but I need to learn how to do it.

Will91Jeeper wrote: I have the attenuator to test the injector pulse but I need to learn how to do it.

Connect your signal lead with the attenuator attached to the control side of the fuel injector and the ground lead to B-. The control side is the wire that is not powered up when you disconnect the injector and look for voltage at the harness side of the connector. Pay attention that KOEO there will be voltage present only a couple of seconds, thereafter the ASD relay will shut off power to coil and injectors. Usually the feed wire`s color is the same on all injectors and the controlwires are different colors

Choose a time base of 1ms/div and a voltage range of 10 V/div (or whatever range you feel comfortable with to get a usable capture). Set a trigger on the falling edge around 6 volts and the injector waveform will show up.

Good newsss!!!! Used the jeep today, no case of no-start but I think I've found the P0443 problem. I tried to wiggle the pcm connector and the evap solenoid suddenly started to tick.
The next days I'll try the oscilloscope like you suggest, so in case of no-start I know what to look for but in the meantime how do I know if it's a bad PCM or a bad connector? How do i test the connector?

Out of curiosity, have you unplugged that PCM connector and taken a closer look at the connections on both the connector & PCM? You should inspect them with a flashlight & look for any damage or corrosion.

Connector and pcm pins seem fine

Used the Jeep today and still P0443 code, tryed to wiggle connector but didn’t work today so I tried this, I heated up the pin 20 the evap purge valve control pin, pulegged in the connector and now works if I wiggle it. I believe it’s a bad pin solder in the pcm


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