Cross posted in other forums and so far have not found the issue or way to resolve.

I purchased a used pcm and sent it off to get a tune added. Once it arrived I installed it. First issue I had was during case relearn I received an error saying the tech2 lost connections. I figured I must have accidentally bumped the connector as you must put one foot on brake and one on accelerator. Restarted process and completed with no issues.

i then took a long (200 mile) test drive to feel the performance improvements and give the obd a chance to run through self diagnostics. None of the test ran. Also while driving the radio turned itself off for a few seconds then back on several times. After the second time I kept an eye on the dash to see if anything else was going on. I noticed that when the radio, whether on local Channels or xm, went off it appeared to loose complete power (no clock). When it comes back on it always reverts to fm band. The radio also retained all of the channels programmed and correct time though.

Also while driving I left the actron scan tool on to watch live data and drive cycle monitors. Multiple times it would loose connection with obd requiring me to restart tool. It is powered by obd and never lost power, just connection with CAN bus.

When I got home I put the stock PCM back in and everything is back to normal. Poor performance, shift points and all. No gremlins.

I contacted tuner to talk about issue. I figured that I must have bought a bad second hand PCM (tried saving a few bucks) so I ordered one from tuner and he put the tune on theirs for me then mailed it out. Once it arrived I installed that one and same issues as before.

After driving several days of the obd self test have all run except the evap The only codes I have been getting are “U” codes. The more I drive the less codes I get but radio continues to appear to lose power. Any ideas on how to resolve. Anyone else run into this after pcm tune. 2007 h3 i5 and never had issues before and still have no issues with stock pcm installed.

Also so as an FYI I ran every test that tech2 has and everything on bcm, digital radio module and radio module show all good with no codes or issues.

 

Did you disconnect your battery when you swapped them out? Just a long shot but I'm throwing it out there. When I had issues with my head unit randomly losing power (but not resetting), one of my battery terminals didn't have a proper connection, replaced with a better terminal and the problem stopped

 

Yeah I have three pcms now. One stock and two tuned. Disconnect the battery and remove one and install other then reconnect the battery.

With the stock pcm no issues other than crappy shift points and performance. With either tuned pcm radio appears to lose main power stays blank for a couple seconds them comes back on.

The other night while driving when it’s dark out the lights in buttons stayed light. Also it retains channels programmed and time still set but radio still cuts off and display goes blank (no clock). So it is keeping some power but acts like it reboots.

 

I went ahead and checked for codes again using tech2. All is clear on pcm but found these on bcm. Keep in mind with stocked tuned pcm I don’t get these. I have looked each up but can’t find anything on trouble shooting each

U1137 lost communication with satellite digital audio reception system
U1151 lost communication with onstar
U1016 lost communication with engine control system
U1064 lost communication with body control module
U1128 loss of IRC communication

I am now thinking maybe one of the three plugs on pcm is not making a perfect connection. Any clue on which one I should tear into and any suggestions on how to remove black plastic cover on plugs to check wires?

 

I don’t want to speak too soon but I think I may have figured it out. On the gray plug (c3) on the inside is a small green tab that broke off and fell on top of the rubber ring. This prevented the plug from seating on the bottom pins. Pulled the broken tab out, reseat the rubber seal and reinstalled the pcm. Radio did not lose power on 40 mile drive. I will take it out again to see how it does.

 

I hope that is all it was.
Fingers crossed.