Greetings Forum Members!

Hoping there is someone who has some insight on how to resolve an issue we are having with our 2016 Suburban LT. For the record, it is equipped with the standard 5.3L V8 ECOTEC3 engine, 6-speed automatic transmission, 4WD with two-speed transfer case, and towing package. I list these features as they all contribute to making the drive train unique to this particular vehicle, and I'm pretty sure the symptom we are experiencing is either within the engine/transmission management system or possibly another related system.

Here's the issue: A severe hesitation upon acceleration from light to moderate throttle at vehicle speeds between 15-25 mph; there are NO FAULT CODES stored, and no warning indicators or messages present. The symptom is chronic, but not consistent. That is, the symptom occurs with regularity, but not at all times. Our local dealer is unable to correct the issue and spends little time attempting to duplicate the symptom. But, the hesitation is so severe that it represents a safety concern, especially when changing lanes with a vehicle bearing down upon us. YIKES!

Also of concern, and possibly related, we have experienced some transmission shifting issues - hard 4-3, 3-2, 2-1 downshifts. Most recently, we experienced a situation where driving at highway speed of around 60mph and accelerating to overtake another vehicle, the transmission shifted from 6-5, 5-4, and then would not up-shift on release of the throttle, causing the engine to continue to rev around 5,000 RPM. It finally up-shifted *AFTER* I applied pressure to the throttle TWICE, finally shifting into 6th gear. Note this symptom has happened just one time, though it is somewhat of a troubling symptom as it may be a signal of a larger problem.

Apparently, there are no service bulletins from GM regarding this matter, though there is a "PIP" (unknown acronym) number 4112Q that addresses a similar concern. This PIP does NOT address the specific symptom we are experiencing. Again, the dealer has been of little help.

Any help from forum members is GREATLY APPRECIATED!

Thank you!

 

With the vehicle being throttle by wire, things I would inspect or be suspicious of are:
the accelerator pedal position sensor
sticky throttle plate motor
Do keep in mind if you romp right down on the accelerator pedal it will not immediately respond, there will be some lag.

 

The vehicle is now out of warranty, and neither of two dealers nor General Motors were any help. The conditions persist, making this the worst vehicle I’ve ever owned. A very unpleasant ownership experience. I would NOT recommend this vehicle type equipped in this manner, nor would I recommend a GM vehicle now knowing how poorly they stand behind their product.