I thought that I would take care of a three year old oil leak since I have repaired my misfire problem a month ago (Optispark and two fuel pumps in another thread).
So I replaced my intake manifold gaskets which was an easy job I used Felpro gaskets (the gaskets do cover part of the cylinder head intake port roof but so did the OEMs that I removed).
I let the car sit for two days with the battery disconnected to let the RTV cure before I started it up. When I reconnected the battery the PCM took a dump. I got a Service ASR and ASR Off light after start up, the car ran pretty rough too. So I went over everything, I was careful with all the wiring and everything was connected properly. Again this was a straight forward job that I have done on many of my previous cars.
I pulled the code and the only code was set in the chassis C0064 Throttle Position Signal Malfunction. I took out the FSM went through the diagnoses and the flowchart kept pointing to the EBTCS behind the drivers seat. I finally figured out that I had 195 ohms between the Reference 5 volts and ground, not exactly a short but certainly way too much of a load for the Reference 5 volts.
I disconnected all my sensors that used Reference 5 volts one at a time to see if the 195 ohm resistance would disappear. Nothing changed!!
I finally disconnected the Black connector going to my PCM because this is where the Reference 5 volts comes from. Bingo infinity no more 195 ohms. I reconnected all my sensors back up and the meter still showed infinity.
I went back to the PCM disconnected it from the car and measured pins 28 and 29 to ground, 195 ohms. By disabling pins 28 and 29 on the PCM and using an external 5 volt power supply source to replace the PCMs Reference 5 volts I can get the car working properly with no codes and the engine runs fine (doing this showed only a 148mA draw on my external power supply so at least the rest of the sensors and wiring are okay).
My PCM fried and it must have happened when I reconnected the battery after 2 days of sitting disconnected, it was running fine up to this point. Why did the PCM do this I have no answer.
I found the IC that is responsible for the reference 5 volts. It is marked "70306 Singapore". I only found one place that shows that they sell it https://au.utsource.net/itm/p/1007157.html
I ordered some but I have my doubts they are going to deliver.
Does anyone have any suggestions where I can obtain one of these? My last resort is to buy another PCM and remove the IC from that one and use it on my PCM.

 

I had the same 15 Pin IC 70306 chip fail on a 2004 GMC Sierra 2500HD Allison Transmission. Chip is getting hot with no load. I had to find the chip in another module that was trashed. Hope you found you one and fixed your problem