Vacuum is good, solenoid is good ad tumblers are not sticking. When I ground neg wire going to the vacuum solenoid the tumblers close and stay closed as long as I keep the ground.
So my problem has to be upstream from the vacuum solenoid which as far as I know is just the wire harness to the PCM and the PCM itself.
Any other ideas?
Based on my clear understanding of the same-similar system in older cars (2004-2007) your testing and descriptions make complete sense, and I agree with you.
The fault should lie within (that wire) the wiring from the IMRC solenoid to the PCM, -or the PCM is defective. You should refer to the 2010 wiring diagrams and ring-out (test) the associated wiring.
If anyone here has the needed 2010 wiring diagram PLEASE help him out.
For 2004, the IMRC wiring info is inside diagram #26 "Engine Controls".
Most car repair shops have access to the "pin-out" information that you need. Stop by a local garage and ask nicely, they might give you the needed pin-out info for free.
If the wiring tests pass, I would still caution you from replacing the PCM without addition thought and testing. My light suspicion is a different problem: the IMRC Actuator and associated wiring. The PCM will not engage ((ground)) the IMRC Solenoid if the Actuator does not have communication to the PCM. So, the PCM effectively "watches" the Actuator to see if the actuator is working properly, and only then does the PCM allow the solenoid to engage. The exception to this rule is at first key-on, engine-on. So, it should work on first power-up, but after that, if something is wrong, it will get stuck in a failed state.
Once the IMRC system has failed, ((aka -the PCM fails the continuous IMRC Actuator self-check)) the PCM will not allow the IMRC system to work again (will not ground that solenoid) UNTIL you turn the engine and key off.
Sorry if I am rambling-on,... I am unsure about the 2010 wiring, and also do not know the PCM (firmware) operational characteristics of the IMRC system for the 2010.