Possible ECM or Loom issue causing #6 misfire?

[Red Beard the Frozen]

2009 sierra 5.3 with AFM.  Big picture is cylinder 6 misfire.  Its getting fuel and spark, awesome compression.  Rocker arms move on turning over but stop on startup, not a stuck lifter.   Quick breakdown of what I have accomplished so far.  I plugged a buddies computer in and we deactivated each solenoid, everyone but the one for 6 would click on and off.  The solenoid for 6 was silent and unmoving.   Next step was I pulled the VLOM, checked all the solenoids and they will open an close under power of a 9v battery.  So solenoid functions ok.   I checked the resistance and they all look good.  I assumed stuck solenoid so I put it back together and still a misfire on 6.  My next step was to tear it down again and check the 5 pin connection that goes to the VLOM.  My next assumption was that pin 4(for cylinder 6) was grounding out.  I checked continuity on all ground pins by putting the tester in the connection pin hole and the other on the block.  Pin 4, while it wasn't enough to make my tester beep, showed a small amount of pass through.  This would explain why the solenoid engages upon the key turning on.  It appears to be permanently grounded.  So a couple questions regarding this issue.

 

1. Has anybody heard of ECM issues causing an AFM solenoid to permanently ground?   

2. Will Disabling AFM negate the fact that the solenoid is grounded as long as the connector is unplugged?

2B. If the easy solution is to disable, what do i need to do to the VLOM regarding oil flow.

3.  I can test continuity in the wire to the computer but I can't find the pinout for that particular connection, anyone have one floating around?

4.  Biggest question of all, WHY GMC WHY?  The LS was such a good motor!!!!

 

[swathdiver]

On 1/21/2020 at 2:31 AM, Red Beard the Frozen said:

2009 sierra 5.3 with AFM.  Big picture is cylinder 6 misfire.  Its getting fuel and spark, awesome compression.  Rocker arms move on turning over but stop on startup, not a stuck lifter.   Quick breakdown of what I have accomplished so far.  I plugged a buddies computer in and we deactivated each solenoid, everyone but the one for 6 would click on and off.  The solenoid for 6 was silent and unmoving.   Next step was I pulled the VLOM, checked all the solenoids and they will open an close under power of a 9v battery.  So solenoid functions ok.   I checked the resistance and they all look good.  I assumed stuck solenoid so I put it back together and still a misfire on 6.  My next step was to tear it down again and check the 5 pin connection that goes to the VLOM.  My next assumption was that pin 4(for cylinder 6) was grounding out.  I checked continuity on all ground pins by putting the tester in the connection pin hole and the other on the block.  Pin 4, while it wasn't enough to make my tester beep, showed a small amount of pass through.  This would explain why the solenoid engages upon the key turning on.  It appears to be permanently grounded.  So a couple questions regarding this issue.

 

1. Has anybody heard of ECM issues causing an AFM solenoid to permanently ground?   

2. Will Disabling AFM negate the fact that the solenoid is grounded as long as the connector is unplugged?

2B. If the easy solution is to disable, what do i need to do to the VLOM regarding oil flow.

3.  I can test continuity in the wire to the computer but I can't find the pinout for that particular connection, anyone have one floating around?

4.  Biggest question of all, WHY GMC WHY?  The LS was such a good motor!!!!

 

No code P3400 or P3441?  Yes, a fault in the ECM can cause a specific solenoid to short.  Send me an email, I've got a pinout somewhere.  [email protected]

[OlRed87]

Hey Red Beard. I know you posted this a while ago but did you ever get this fixed and if you did what was the fix. I have the same problem with an 11 5.3l vin 3.