2007 GMC Denali stalls after towing

[Doubeleive]

While its been few months since this post, this information can help others with this problem. While sensors, transmission, etc. can cause this , the most common cause of this (hot stall at low speeds & idle, no start when hot) has been identified and solved elsewhere. Specifically as it applies to 2007-2008 6.2L L92 engines, but it may apply to others as well.

This is a very common problem on 07-08 6.2L engines: The problem is related to a combination of low hot oil pressure at low engine speeds, and the cam phasor. The ECM commands the cam phasor to exteme angles at highway cruise engine rpms, to get a small fuel economy increase. The commanded cam angle is so extreme, that the engine would die at idle and/or not start if it were to stay stuck at that extreme angle. You can see where this is going. Low hot oil pressure, prevents the cam phasor from going back from the highway fuel economy phase angle to an angle suitable for low rpm and idle operation. The engine then stalls exactly as described, and may not restart for quite some time. While low hot oil pressure can be caused by oil pump pickup tube O-rings, etc ... in 2007-2008 6.2's are known for cam bearing wear issues that cause low hot oil pressure.

First, check your hot oil pressure. Remember that oil temperature takes longer to heat up than engine coolant temp, and towing will get it hotter still. Less than 20psi at hot idle could be a problem for the cam phasor operation.

So what can you do about it? One element is to increase your hot oil pressure: Switch to an oil that has excellent viscosity and film strength at high temperatures (for example Amsoil Signature series 5W-50), and keeping your engine as cool as possible. The second element is to find a tuning shop, with HP tuners, that can program the Cam phasor to stay at a fixed angle, so it never gets out of whack in the first place. This can be a good solution, because the oil pressure may be too low to actuate the cam phasor, but still high enough to operate the rest of the engine reliably. While I haven't had the problem, I'm doing the first part of this as a preventative measure.

so maybe the fix for people with this problem is a oil cooler, I have never had this issue myself but I have monitored my oil temp while driving "very spiritedly" on purpose just to see what my oil temps go up to and surprisingly they stayed around 180deg no matter how hard I tried to make everything hot even for a extended period of time, I was surprised it did not go up like the transmission temps will. If anyone is experiencing this issue currently I would try connecting a scanner or obd device that can monitor the oil temp and see what those temps are when you stall out.

 

[tgui]

While its been few months since this post, this information may help others with this problem. While sensors, transmission, etc. can cause this; perhaps the most common cause of this (hot stall at low speeds & idle, no start when hot) has been identified and solved elsewhere. Specifically as it applies to 2007-2008 6.2L L92 engines, but it may apply to others as well.

This is a very common problem on 07-08 6.2L engines: The problem is related to a combination of low hot oil pressure at low engine speeds, and the cam phasor. The ECM commands the cam phasor to exteme angles at highway cruise engine rpms, to get a small fuel economy increase. The commanded cam angle is so extreme, that the engine would die at idle and/or not start if it were to stay stuck at that extreme angle. You can see where this is going. Low hot oil pressure, prevents the cam phasor from going back from the highway fuel economy phase angle to an angle suitable for low rpm and idle operation. The engine then stalls exactly as described, and may not restart for quite some time. While low hot oil pressure can be caused by oil pump pickup tube O-rings, etc ... in 2007-2008 6.2's are known for cam bearing wear issues that cause low hot oil pressure.

First, check your hot oil pressure. Remember that oil temperature takes longer to heat up than engine coolant temp, and towing will get it hotter still. Less than 20psi at hot idle could be a problem for the cam phasor operation.

So what can you do about it? One element is to increase your hot oil pressure: Switch to an oil that has excellent viscosity and film strength at high temperatures (for example Amsoil Signature series 5W-50), and keeping your engine as cool as possible. The second element is to find a tuning shop, with HP tuners, that can program the Cam phasor to stay at a fixed angle, so it never gets out of whack in the first place. This can be a good solution, because the oil pressure may be too low to actuate the cam phasor, but still high enough to operate the rest of the engine reliably. While I haven't had the problem, I'm doing the first part of this as a preventative measure.

Having replaced my 08 6.2 pickup seal and seen a noticeable change in oil pressure, I agree.

 

[Geotrash]

While its been few months since this post, this information may help others with this problem. While sensors, transmission, etc. can cause this; perhaps the most common cause of this (hot stall at low speeds & idle, no start when hot) has been identified and solved elsewhere. Specifically as it applies to 2007-2008 6.2L L92 engines, but it may apply to others as well.

This is a very common problem on 07-08 6.2L engines: The problem is related to a combination of low hot oil pressure at low engine speeds, and the cam phasor. The ECM commands the cam phasor to exteme angles at highway cruise engine rpms, to get a small fuel economy increase. The commanded cam angle is so extreme, that the engine would die at idle and/or not start if it were to stay stuck at that extreme angle. You can see where this is going. Low hot oil pressure, prevents the cam phasor from going back from the highway fuel economy phase angle to an angle suitable for low rpm and idle operation. The engine then stalls exactly as described, and may not restart for quite some time. While low hot oil pressure can be caused by oil pump pickup tube O-rings, etc ... in 2007-2008 6.2's are known for cam bearing wear issues that cause low hot oil pressure.

First, check your hot oil pressure. Remember that oil temperature takes longer to heat up than engine coolant temp, and towing will get it hotter still. Less than 20psi at hot idle could be a problem for the cam phasor operation.

So what can you do about it? One element is to increase your hot oil pressure: Switch to an oil that has excellent viscosity and film strength at high temperatures (for example Amsoil Signature series 5W-50), and keeping your engine as cool as possible. The second element is to find a tuning shop, with HP tuners, that can program the Cam phasor to stay at a fixed angle, so it never gets out of whack in the first place. This can be a good solution, because the oil pressure may be too low to actuate the cam phasor, but still high enough to operate the rest of the engine reliably. While I haven't had the problem, I'm doing the first part of this as a preventative measure.

Thank you for coming here and posting this key insight. Makes perfect sense.

 

[HD_LS]

You're welcome. Glad to help when I can.

 

[patsfan123793]

Thanks to everyone who has contributed to this thread so far. I've been digging into this issue on my 07 Yukon Denali- 125k miles. Some facts on my vehicle-


10k miles on rebuilt transmission
Engine operating oil pressure is measuring roughly 10-12 PSI at idle, 20-30 psi on highway from 2k-3k rpm. Oil Pressure went up after oil change by a few psi each.
I have replaced the Cam position sensor
Mobil 1 5W-30, M113A Filter (change described in timeline below-)
After stall failure described in this thread I have the most luck with waiting 20 mins and flooring the accelerator when I go to start it again.



Stalling has occurred on 4 occasions-

1. Mid November- First after a 2 hour drive on the highway as I got off the exit it started to sputter a bit. Parked it for an hour. Went to start it up and it just spun the starter motor as described many times in this thread. Floored the accelerator and got it to fire up. Drove two hours on the highway home without issue
2. One month (Today)- Bought a trailer that weighs about 2500 pounds. First time it happened 15 minutes after being in tow mode through some back roads at less than 40 miles per hour as I stopped at a stop sign.
3. Second time today- as I completed the 30 minute journey from item 2 as I came off the highway in Tow Mode.
4. Oil needed to be changed, so I changed it hoping it would help solve the problem. I change the oil and filter at this point
5. Third time today- as I bring the trailer to its final destination just as I coast into the driveway after a 25 minute drive in tow mode.
6. Drop the trailer off and I drive it 30 mins back making 2 additional stops and have no issues whatsoever

I had hoped and planned to take this new trailer on a road trip this weekend. I have until Saturday to get it ready. Any recommendations on some steps I can take to reduce my risk on taking this trip?

Any and all feedback is appreciated.

 

[upnorth76]

I hope this helps some of you...


Ok people. Here it is. The REAL PROBLEM for me and most likely for 90% of you out there is this!!!

Bit of background. I’m a licensed tech in Canada 21yrs. Experience. Worked at Dealerships for 17 years including GM for 4yrs.... anyway....

My truck: 2007 Denali: 6.2L - 6L90 trans. 385,000km ( 240,000 miles )

First, my symptoms: random stalling/ NO RESTART after towing/HOT. Then after awhile random stalling NOT TOWING, turning left/right etc...
At first wasnt setting any codes other than a random shift solenoid code in trans. Then later on setting low oil pressure code P0521. ( prob have cracked o-ring on oil pick up tube )

Tried new fuel pump relay and thought I had fixed it... nope. Then replaced fuel pump w/ ACDELCO unit... thought it was good... nope.

THEN TRIED: cleaning battery connections, clean 175A fuse connections on pass firewall, checked PCM pins for backing out/ added dielectric grease to help prevent “ fretting” as/per GM TSB, removed underhood fuseblock/ JUNCTIONBLOCK, checked all pins in base mounted connectors/ looked good/ applied dielectric grease to all, added trans “ medic” additive to trans fluid, test drove to get trans to oper. temp. then serviced trans. using proper fluid ( this is to address the issue related to suspected TCC CLUTCH/ solenoid/ valve sticking ) I didn’t suspect this because when that happens you get a noticeable LURCH/Bucking when Yukon stalls out and I think most people ( including me ) aren’t getting the lurching/ stalling.
ALSO added GUNK ENGINE FLUSH and 1L ATF ( atf in engine crankcase is a great cleaner because atf contains lots of detergents ) to crankcase to flush engine lube system. This was to address possible VCT valve/ phaser sticking causing stalling after coming to stop from hwy. speed/ heavy loaded condition. Serviced engine w/ 0w40 Mobil 1...

DID ALL OF THIS IN ONE NIGHT... because I didn’t have time to mess around doing it one at a time to see what fixed it... ANYWAY... NOTHING WORKED. Drove for long test drive at high speed, seemed ok, thought it was fixed, wife was driving it two days later in stop and go traffic and it stalled again.

This time ENGINE POWER REDUCED MESSAGE AND ENGINE OVERTEMP. MESSAGE CAME ON IN CLUSTER.

So then I finally broke down and fixed what I suspected to be the REAL problem all along but is really EXPENSIVE!!

Faulty underhood fuse block w/ integrated PCB ( printed circuit board ). Circuit board cracks, and various circuits open up when underhood TEMPS get HIGH!!

Costs $850+tax at the dealership in Canada. Will cost you about $600 in the U.S.

Replaced this and haven’t had any problems since then.

Have had TONS of issues which these while working at the GM dealer but didn’t want to try it first since they are pricey $$$.

Fixed stalling issue and reduced power message etc...

I think this is probably the problem for most of you guys... I Hope this helps someone.

 

[upnorth76]

Thanks to everyone who has contributed to this thread so far. I've been digging into this issue on my 07 Yukon Denali- 125k miles. Some facts on my vehicle-


10k miles on rebuilt transmission
Engine operating oil pressure is measuring roughly 10-12 PSI at idle, 20-30 psi on highway from 2k-3k rpm. Oil Pressure went up after oil change by a few psi each.
I have replaced the Cam position sensor
Mobil 1 5W-30, M113A Filter (change described in timeline below-)
After stall failure described in this thread I have the most luck with waiting 20 mins and flooring the accelerator when I go to start it again.



Stalling has occurred on 4 occasions-

1. Mid November- First after a 2 hour drive on the highway as I got off the exit it started to sputter a bit. Parked it for an hour. Went to start it up and it just spun the starter motor as described many times in this thread. Floored the accelerator and got it to fire up. Drove two hours on the highway home without issue
2. One month (Today)- Bought a trailer that weighs about 2500 pounds. First time it happened 15 minutes after being in tow mode through some back roads at less than 40 miles per hour as I stopped at a stop sign.
3. Second time today- as I completed the 30 minute journey from item 2 as I came off the highway in Tow Mode.
4. Oil needed to be changed, so I changed it hoping it would help solve the problem. I change the oil and filter at this point
5. Third time today- as I bring the trailer to its final destination just as I coast into the driveway after a 25 minute drive in tow mode.
6. Drop the trailer off and I drive it 30 mins back making 2 additional stops and have no issues whatsoever

I had hoped and planned to take this new trailer on a road trip this weekend. I have until Saturday to get it ready. Any recommendations on some steps I can take to reduce my risk on taking this trip?

Any and all feedback is appreciated.

Please read my post above...

 

[08grey]

Pics of said board?

Sent from my SM-G973U1 using Tapatalk

 

[upnorth76]

If you want pics of the cracked PCB it will be a while as I would have to cut the JB apart with a grinder and look for it. I’m a working tech and I don’t have time for that. All I know is it fixed my Yukon and it has fixed many more GM TRUCKS with a plethora of various electrical issues; from headlights not working to stalling to engine overheating... Me stating that the issue is a cracked PCB is relayed info from just being told by other techs that have repaired various electrical issues by replacing the underhood fuse block over the years... starting in 2007 w/ the GMT800 platform. Cheers, hope some of you that haven’t ever been able to repair your stalling issue will get closure with this info. It can drive you to insanity when nothing fixes an issue and “ normal “ diagnostics turn up nothing...


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[Fless]

starting in 2007 w/ the GMT800 platform

Do you mean the GMT900 platform?