2010 v6 camaro keeps frying computer

2010 Camaro 3.6l V6 automatic

The issue at hand is the PCM keeps going bad and causes fuse #5 in the under hood fuse block to blow.  In the underhood fuse block there are two fuses dealing with the PCM number 5 and number 20.  Number 20 is fine it doesn't blow and power through that fuse is good all the way to the connector to the PCM. This is the 3rd computer and now I'm in deep with this one I have to get it fixed.  I find it hard to believe 3 different computers all failed in the same exact way all 3 times.

1st time about a year ago.  go to start the car and nothing.  From under the hood you could hear clicking then nothing.  No start no crank and the check engine light would flash very rapidly approximately 7 to 10 times per second.  During initial diagnosis found fuse #5 blow.  Reinstalled fuse fuse popped with in a few second.  during that time the throttle body would quickly move from full close to full open back to full close very rapidly.  It was quick enough to hear it bang against the internal stops.  While throttle body was doing its thing there was a relay clicking in the under hood fuse block but was unable to identify which one.  Checked all fuses again and found only fuse 5 to be bad.  At fuse 5 used test light connected to ground to determine which pin was battery power and which pin was connected to pcm.  With test light connected to battery positive connected test light to fuse 5 pin going to pcm and light was fully lit.  Disconnected both connectors from PCM and light went out.  This rules out short in harness and thus a bad computer.  Checked all powers and grounds at PCM connectors with a 1 amp test light all good. Put "refurbished" computer from flagship one in, against my wishes and desires.  Programmed pcm and did key relearn and vehicle started and ran fine but security light was flashing.  No codes other than a key code, can't remember the exact code.  

No issue until July of last year same exact failure in the same exact way followed same exact procedure and condemned PCM again.  Flagship pulled through and set another "refurbished" computer.  Programmed did key relearn and car drove off with no codes,except a key code, and still flashing security light.

Today same exact problem but this time it occurred while driving.  Initial issue was service stability trac message on DIC while driving, then reduced engine power.  Engine shut off and upon attempting to restart same condition.  Clicking of throttle body with an unknown relay clicking and fuse 5 blown.  Two times piror to this happening in the last week there was a one time nostart(no crank no start condition).  go to turn the key and just a click, same sound as a bad starter solenoid.  Release key and engine would start with no problem.  Not sure if that is related or not but I don't want to leave anything out.   

During these episodes of blowing fuse 5 no codes could be retrieved from PCM with no comm codes with PCM in ABS, TCM, and air bag module.

I will be putting in a new AC Delco computer it this time but its a week out.  So I have a week to figure this out.  I believe there is something wrong with the throttle body but I'm not 100% sure.  At the moment I do not have access to service data but I will be purchasing a subscription to Mitchell diy and doing what checks I can after work.  Any one ever ran across this I am stumped. As you can immagie I can not afford to get this wrong again, assuming there is another underlying unfound issue. 

crasher88, I know it sounds irresponsible, but I'd consider putting a bigger fuse in the F5U socket and see if the PCM will power up. Or a circuit breaker, either way. The hope would be that the higher current supply would allow the PCM to stay powered and help ID an output that could be causing repeat failures. 

I wouldn't get too stupid with it. 25A, maybe. What's the worst thing that could happen? Smoke the PCM? Too late for that. Smoke an output? If there's an output causing the PCM failure, it's better to know about it now. 

If the PCM will set codes, that'll help you narrow down your suspects.

There's really only a few high current outputs that are power side controlled by the PCM on that engine. Injectors and the high pressure pump come to mind. And the throttle, like you noted. Those are my first suspects. 

update

.tinkered with it a bit this morning before work. hooked computer back up and for s&g took ohm meter to fuse 5 and placed other end to plenum and got near perfect continuity <.3 ohms.

Attached is a picture of the fuse block and the powertrain relay sockets drawn in for reference. Pin 30 and 85 are always hot, confirmed with test light. 86 is turned on by PCM and can be actuated with a test light from the x2 PCM connector. Checked relay in the fuse block and out. Not concerned with the relay. Once relay is tripped it supplies power through pin 87 of relay to fuse 5, 7, 8, 9, and 10. After thinking about it all day and looking at wiring diagrams I decided it would be best to do resistance check from the x1 and x2 connectors for the PCM. I hate resistance check but at the moment I think it is the only thing I can think of and need to find some direction.

After I got home from work began working on it again and pulled out my ohm meter and began doing my checks. Depending on the circuit I was check I went in the connector though the component and out to the corresponding pin on the same connector for PCM, or from pin 87 of the pcm relay through the component and to the pin on the connector and addition checked to ground on the engine block(plenum). All of these test were done on the x1 PCM connector. It is a 96 pin connector that is on the PCM.

x1
pin 1 exhaust bank 1 vvt solenoid to pin 87 7.3 ohm
pin 2 intake bank 1 vvt solenoid to pin 87 7.4 ohm
pin 3 to pin 4 #6 fuel injector 1.7 ohm(spec if 1.3-1.73)
pin 5 to pin 73 high pressure fuel pump pressure control solenoid .7 ohm(yes that is  zero​.​seven  ohms of resistance) I could find no specifications for this in Mitchell but that number peaked my attention
pin 6 purge solenoid to pin 87 16.9-17 ohm
pin 7 bank 1 intake cam position signal (wasn't sure how to test)
pin 8 no used
pin 9 bank 2 exhaust cam postion signal(wasn't sure how to test)
pin 10 charge indicator control(alternator control) meter would not stabilize all kinds of weird readins when connecto to engine 
pin 11-12 no used
pin 13 coil 2,4,6 feedback to pcm 5.1k ohm to engine 
pin 14 not used
pin 15 5 volt ref 3 OL m ohm to block
pin 16-17 not used
pin 18 vacuum assist pump relay control OL M ohm to engine
pin 19-20 not used
pin 21 trans temp sensor(wasn't sure how to test
pin 22-23 no used
pin 24 to pin 48 throttle motor 2.6 ohm
pin 25 bank 2 exahust vvt solenoid 7.4 ohm to pin 87pin 26 to pin 27 #3 fuel injector 1.7 ohm
pin 28 to pin 29 #5 fuel injector 1.7 ohm
pin 30 generator field duty cycle 11K ohm to engine
pin 31-32 not used

as it was getting dark my last test was with a test light connected to battery positive and connected first to pin 5 then pin 73 for the fuel pressure solenoid and it did NOT light up. This rules out any short in the harness for that solenoid but I still don't like the resistance measurment.that was all I was able to do after I got off work before the sun set. Any inputs or feed back?

did some more testing and I have found something.

With pcm installed all fuses can be installed with no issue only when the key is turned on is when fuse #5 will blow. So the following test were completed with all fuses installed and PCM removed from vehicle. X1 and X2 connector for PCM were disconnected.

took my test light connected it to battery positive and probed pin 87 for PCM relay. Confirmed my test light was installed correctly with a volt meter checking for voltage on the 5 fuses that are powered on by the PCM relay. Once test light was connected test light was on. Not fully but it was lit up. Confirmed voltage drop over my test light and hooked up my ammeter to my test light as well. 130 mA when test light was on(typically with system voltage about 13.5-14 volts my test light will pull nearly 230 mA). With research found these 5 fuses feel all 6 coils, all 4 vvt solenoids, all 4 O2 sensor, and purge solenoid. Through a combination of trial and error I could make the test light go out by pulling fuses. Looked the fuses up on a wiring diagram and started experimenting. I was able to disconnect 5 out of the 6 ignition coils and one of the vvt solenoids on the driver bank(not sure which cam it was for wasn't worried about that at the moment). Once light went out verified with ammeter and with voltage drop that there was no current flowing any more.

Can some one confirm my findings, and dissect what I did and see if you can find any holes in my process. I am having a hard time buying 5 ignition coils and a vvt solenoid are bad and causing this issue. If my test are correct and these parts are bad I am more than willing to bet these bad parts are just an indicator of something else being bad(ie alternator)

Sorry if you said so and I missed it, but did you disconnect the HPFP solenoid, and if so, does the ECM fuse continue to open?

No I did not disconnect the hpfp solenoid when I was doing my testing. And I did not attempt to turn the key on with everything unplugged. It was getting late and the sun had already set. I have no place to work on the car inside so I was forced to quit.