NEED HELP 2012 Yukon stalled after startup, have codes

[gmcman]

I wanted to ask this here first since there are a few here with a good knowledge of the electrical/canbus system. I have no issues with the vehicle, until a couple days ago and again today. I think this first part is unrelated (MAF harness) but going to include it along with the backstory so bear with me.

Two weeks ago, I had some time and a spare vehicle so I did some preventative and necessary work to the Yukon. I had caught a small brief coolant odor at a light and again at another light, so with 155K and the OE water pump, I was going to change all that, pump, hoses, T fittings, etc. I also had a small front main seal leak and the oil cooler lines had a small leak, so all that was on the docket.

For the coolant, I didn't see any leaks, but definitely caught the odor. When removing the pump I think I may have found the culprit, looks like the gasket leaked into a bolt hole but all is good now.










I don't want to miss any steps in hopes it may be a necessary detail in diagnosing.

So before starting I removed the battery ground, as well as the MAF connector to remove the air tube. I also removed the starter to install a flywheel locking tool to get the balancer bolt back on.

When replacing the oil cooler lines, it was a snug fit even with the front diff lowered slightly but had to snake it past one of the ground wires which looked a little rough. This is on the LH side of the block, near the front. I did not disturb it but it was in the firing line of the cooler tubes.






Once I finished everything up, I went to start it and it fired up then died, I then remembered I forgot to reconnect the MAF harness and had a code for the IAT circuit. I reconnected the harness, cleared the code and it started and ran.


This is where it gets interesting.....fast forward a week, has been driving perfect.. and in my driveway I used the factory remote start, it fired up and immediately stalled. I popped the hood and checked the MAF harness and all was good, battery cable was tight, nothing looked out of place. I then tried to restart it and it started, but I had no working dial gauges and this made me think the ignition switch. Also when it started the service stabilitrak, TSC and another driveline associated light popped up on the DIC. I shut the engine off and tried to restart again and I could turn the key, but no crank, like it was in gear and not P or N. I put it in N and back to park, tried both times, and no crank.

I then checked the codes and had these....




P069E: Fuel Pump Control Module Requested MI

P0700: Transmission Control System MIL Request

U0073: Control Module Communication Bus A Off

U0100: Lost Communication With ECM/PCM

After about 5 min, I tried to restart again and it fired up. I cleared the codes, checked all the grounds at the engine bay but did not check the trans connector or the fuel pump control module as I had to leave on a 2hr roadtrip (each way) which was NOT how I wanted to leave and be worried about. Not the best judgement call but this really seemed like a loose connection or just a glitch.I did check everything I could see, engine ran great, I restarted a few times and no problems.

We did have a ton of rain the last few days, maybe that played a part, but I think removing the starter with a close ground wire, the ground near the oil lines, maybe even disconnecting the battery, not sure but....was too coincidental.

Other than checking the obvious, all the grounds, trans harness, FPCM harness...does this look like another issue? I did read a post in the Tahoe Yukon forum about someone finding bad solder joints inside the FPCM but that member had different codes but similiar symptoms when it stalled but mine did this only once where it wouldn't restart.

Battery has good voltage, 12.3 at rest, pass side ground looks ok.



I'm thinking about crimping some new terminals or maybe replace both harnesses if needed. So far so good, only happened once and never hiccuped after it was running again.

All input appreciated.

 

[mrrsm]

These issues may be sourced to a Problem Battery or a Sketchy Alternator that is NOT Charging properly. Nominal Battery Voltage should be at 12.5 Volts or Better ...so your present resting Voltage is slightly under nominal. You may have a Dead or Dying Cell in the Battery and the only way to reveal it is to Stress Test the Battery with a Load Tester. If your Voltage suddenly drops precipitously, Random Network Codes may set.

Next, Check all of the Fuses on the Circuits that anything to do with the components that you either had to Touch, Move, Tighten Down or R&R, If during your initial Preventive Repairs foray, you Disturbed or S-T-R-E-T-C-H-E-D any Wires inside of any harnesses that had to be tugged or pulled upon, the intermittent nature may reveal a Hidden Broken Wire inside of its Insulation that only occasionally separates enough to disturb the system.

Don't discount the possibility of having Wiring Harness Damage from Rodent Depredation. Get a Bright Flashlight and systematically, examine the entire Engine Harness and remember that this was NOT a problem... until things began to get moved around.

Look for any signs of Nesting Materials, Feces and pools of Dried Urine on any locations down there. If you find anything like this, Do NOT Use Compressed Air to clean things up. North American Deer Mice harbor the Deadly "HANTA" Virus in their Feces, Urine and Saliva, so Use M11 Nitrle Gloves, an N-95 Face Mask and Eye Protection while using Wet Wipes soaked in Bleach Water to clean and dispose of that Crap. The Virus can enter the Lungs when inhaling elevated airborne infected Dust.

About Hantavirus

An overview of hantavirus, how it's spread and how it can be treated.

www.cdc.gov

Go over every single thing you did in your mind and try to remember the sequence of actions you took during the entire time you were under the hood. Following the idea behind "Occam's Razor" that the simplest explanation of anything ...is almost always correct... You may remember doing that "One Thing" that cascaded into these other "No Crank - No Start" issues.

 

[TJBaker57]

I will preface by saying I have zero experience with such systems.

Just read up a bit at Charm.li about the codes you posted and I see there are slightly different wiring versions depending on the presence of RPO HP2 vs without.

So do you have HP2 or no?

Electrical Diagrams — 2012 GMC Yukon 4WD V8-5.3L Service Manual | Operation CHARM

Detailed repair manual for the 2012 GMC Yukon 4WD V8-5.3L.

charm.li

 

[TJBaker57]

If I am understanding the info I read at Charm.li the 1st two codes are generally NOT a fault of the related module. The U0073 and/or U0100 are the likely source of the issue with a loss of communications.

This is some of what I have been looking at;

U0073 — 2012 GMC Yukon 4WD V8-5.3L Service Manual | Operation CHARM

Detailed repair manual for the 2012 GMC Yukon 4WD V8-5.3L.

charm.li

Initial Inspection and Diagnostic Overview — 2012 GMC Yukon 4WD V8-5.3L Service Manual | Operation CHARM

Detailed repair manual for the 2012 GMC Yukon 4WD V8-5.3L.

charm.li

Information Bus: Description and Operation — 2012 GMC Yukon 4WD V8-5.3L Service Manual | Operation CHARM

Detailed repair manual for the 2012 GMC Yukon 4WD V8-5.3L.

charm.li

Electrical Diagrams — 2012 GMC Yukon 4WD V8-5.3L Service Manual | Operation CHARM

Detailed repair manual for the 2012 GMC Yukon 4WD V8-5.3L.

charm.li

 

[gmcman]

These issues may be sourced to a Problem Battery or a Sketchy Alternator that is NOT Charging properly. Nominal Battery Voltage should be at 12.5 Volts or Better ...so your present resting Voltage is slightly under nominal. You may have a Dead or Dying Cell in the Battery and the only way to reveal it is to Stress Test the Battery with a Load Tester. If your Voltage suddenly drops precipitously, Random Network Codes may set.

This could be the issue. After the Yukon sat for about 16 hours, I opened the door to pop the hood and shut the door, only load was the interior lights for about a min or 2. Within the first min of closing the door, I had 12.18V then it slowly rose to 12.32V then finally settled at 12.41V.

The engine fires right up so I never gave it much thought, but about a month ago I was fueling up and left my driver's door open, maybe for 2-3 min. When I sat back down the DIC read "Low Battery". I thought that was odd as I didn't have the exterior lights on, or have "exterior illumination" activated, Engine fired up with no hesitation and I haven't seen it since. The battery is only 3 YO and it's a flooded battery, I recall that these either like or require AGM so I will research that.

Go over every single thing you did in your mind and try to remember the sequence of actions you took during the entire time you were under the hood. Following the idea behind "Occam's Razor" that the simplest explanation of anything ...is almost always correct... You may remember doing that "One Thing" that cascaded into these other "No Crank - No Start" issues.

I agree, and that was my methodical approach, I even wanted to include the cooling system process in case it may even trigger a response from someone reading it, which may involve something I overlooked.

So do you have HP2 or no?

Thank you for the links, I will check them out. No I do not have HP2 and I apologize for not including more pertinent info....mine is a Denali with the 6.2, but I believe most of the 5.3 and 6.2 wiring is the same.

 

[gmcman]

I took the battery to where I bought it in case of a warranty claim. They load tested it and it checked out fine, had just over 12.5V before load testing.

I brought it back, hooked it up, did a starter draw test and 3 times with a hot engine I was around 340-350 amps based on the Fluke clamp meter.

I let the modules rest and after about 30 min I came back and had .097-.102 mA draw on the lead to the fuse box. Maybe it needed more time as that would hog the battery down and I always have sufficient charge.

I did pull fuses and the only one under the hood that made a change was #45, "AIRBAG BATT"

This changed the draw from .100 mAh to .022-.024. If I replaced the fuse it jumped back up. Only after removing and replacing the fuse a few times the draw would settle to around .025 mAh but not before I pulled it...could be coincidence but it's resting now at that same .025ish mAh.

I'll give it some time, but the battery apparently checked out. I also tried a small load test when I replaced the battery and with the engine off, I have about 12.4V, and with the low beams, high beams, seat heater, the voltage would drop to 11.8 and stay there regardless of load as I switched them on and off. Once all were off, it jumped back to 12.25V then slowly climbed to about 12.45V.

 

[mrrsm]

Even though it rarely occurs, Fuses can get micro-cracks that will open up and Break the Circuit when cold...and then sort of "Heal" themselves ...temporarily once things warm up again.

The symptoms you describe with the Parasitic Draw changes in the #45 "AIRBATT" Fuse should prompt replacing it... and then doing a systematic search for whatever is Drawing Down the Battery when in the KOEO status.

 

[gmcman]

Even though it rarely occurs, Fuses can get micro-cracks that will open up and Break the Circuit when cold...and then sort of "Heal" themselves ...temporarily once things warm up again.

The symptoms you describe with the Parasitic Draw changes in the #45 "AIRBATT" Fuse should prompt replacing it... and then doing a systematic search for whatever is Drawing Down the Battery when in the KOEO status.

Doesn't hurt to replace, but I think this was more coincidental...I don't know the sleep schedule of all the modules and the battery has around .022-.025mA drain wihich is pretty good. I don't believe I have a drain that's hogging down the battery, I lost power to a few modules and the ground that's likely near the LF of the motor could be the culprit..not sure though.

The fact I lost the gauges with the engine running points to the ign switch or a module that may have lost power...I would think.