PCM Change, drove 400+ mile, now no-start

[Indi]

2002 Dodge Grand Caravan 3.3 Gas, 120K miles Caravan dies while on vacation. After days of parking-lot trouble shooting lack of power, rough idle & code P0205...ripped apart the top of engine to replace injectors and fortunately tested the wires to #5 injector...finally determined #5 Fuel injector CIRCUIT failed on orig PCM (no pulse through wire, def burned smell in PCM & melted jell spot inside near the edge case). Installed a PCM from junkyard with exact same #'s and put back together the top of the engine ...van started right up and ran great. I drove the van about 400 miles home, then suddenly and without any other warnings, I have a no-start condition the next day. The ONLY thing that was done just prior to the no-start condition was stopping at auto store, removing & reinstalling a molded rubber tube in the top front of the engine that had hardened & deteriorated (goes from the what appears to be a valve cover to the air filter case...maybe to recover fumes or preheat the intake air???). Sadly, they didn't have one, said it was special heat-tolerant rubber, dealer-only item. I just cut off about 2 inches of the badly deteriorated part (part nearest the engine), reinstalled it and drove home to hunt for one on the web. But then the van wouldn't restart about an hour later. At first there was no cranking when I turned the key...the dash & radio lights just dimmed....like the starter solenoid was bad. After a few hours of fiddling with it (inspecting starter, fuses, relays, connectors, etc), I noticed that I could mess around with the brake pedal while holding the key in start position and get it to crank for a second or two (sometimes almost cyclically...like pulses...if I held the pedal in just the right position). Now it cranks without touching the brake pedal, but still no start. - There is no security (always just had a generic, slim key copy). - There is no spark from the ign pack, but prelim tests possible without removing it from engine were good (frustratingly, the connector is in the back, so its not easy testing on the connector contacts). I don't have a tester to see the pulses on the wires (would an LED work?) - Checked connectors on sensors I could reach were tight (even removed the ones I could to see it there was any discoloration or corrosion, then reconnected them). - Tested the ASD & Fuel Pump relay OK, The ASD & Fuel relay both energize when the key is turned on & I hear the fuel pump , but there IS a click somewhere in the panel just about 2 seconds later. - I've done some prelim. testing on the switch (its still exposed), but stopped investigating it when the cranking did start without messing with the brake pedal & the ASD & fuel pump relays seemed to be energizing. - Removed the two big PCM harness connectors from side, inspected for discoloration, sprayed with contact spray & reconnected. - I tried putting orig computer back in and still have the same no start condition (but one code was different). It IS kind-of like some security has kicked in to disable the van. So....here are the codes: Replacement PCM (in the van when no-start condition first appeared): Immed. after Key On: - P0509 (Idle Air Control Circuit High) After 15 secs cranking: - P0443 (Purge Valve Control Malfunction), - P0123 (Throttle Position Sensor Circuit High), - P0118 (Coolant Sensor Circuit High), - P1478 (Cooling Fan Driver) - P1193 (EGR Drive Out Current) - P0509 (Idle Air Control Circuit High) If retried this test a few times & only occasionally get P1193 & P1478, but otherwise consistent results Original PCM reinstalled (the van DID run with it, just lack of power) Immed after Key On: - P0508 (Idle Air Control Circuit LOW....THIS IS DIFFERENT THAN ABOVE) After Cranking 15-20 seconds: - P0123 (Throttle Position Sensor Circuit High) - P0118 (Coolant Sensor Circuit High) - P1193 (EGR Drive Out Current) - P0508 (Idle Air Control Circuit LOW) I've double checked the connector on the Idle air motor. Curiously, the code for it changed from P0509 (Circuit High), to P0508 (Circuit Low) when I put the original computer back in. So what should I try next??? Is there a way to by-pass the Idle Air Control Circuit completely...could it even be the cause of no-start? Its hard to believe that so many sensors or circuits went bad all at once...so am I'm guessing correctly the codes after cranking are the RESULT of the no start condition? I HAVE considered that one branch of the wire harness might be damaged (poss cause of first PCM failure & maybe all the sensors with codes are bundled together somewhere)...but there's no visible sign of damage and I hate to just start digging into it randomly. I do have the Haynes Manual and have been trying all the tests I can find over and over without finding anything terribly suspicious....even put a fresh battery in it....still no start. I vaguely remember removing and cleaning the idle air control motor 2 years ago to resolve some code and get it through AZ emissions, but had no trouble with the Idle Air Circuit since. I'm about to remove it again...maybe just replace it...but $$$ is tight and don't want to just waste it. What should I try next? I'm getting a little tired of walking!!!

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[master tech]

Try replacing the map/baro sensor.

[Indi]

Frsutratingly, changing the MAP sensor didn't remedy the problem. I also check continuity on all the wires between IAC, MAP & TPS sensors and the PCM connector. Still crank (rough crank, not smooth) but no start.

Any other suggestions are welcome.