2003 Yukon Denali XL - Goes into reduced power mode while driving. Able to usually get the vehicle to the roadside or stop and turn off ignition, then reset computer via 5 pedal pumps and the truck will restart. This has been a long-time issue. Happening more frequently. Have replaced Throttle Body 3x'*, new Throttle body wiring harness, Air Mass Flow sensor 3x'*, TPS 1x, Fuel Filter 4'xs. Problem still exists. Vehicle has had weeks of auto electrical specialist evals. Continue to point at either Throttle Body or Air Mass Flow Sensor. Super, super frustrated. The truck as 330,000 miles on it, and I have either done myself or had major R and R done on the vehicle, Engine and transmission overhaul. Looking for any tips that mechanics or owners have had with same or similar problem.

When did this start happening, both in time and mileage?

What codes are stored?

Codes are a must. Seems you go to parts slingers and not a technician. We need to some testing. When a shop replaces a part without testing the parts circuit(*), use them for oil changes only.

I appreciate the response. This issue in one form or another has been recurrent since 2013. Off and on, so intermittent.it has become more recent that the issue has occurred while driving and thus triggering greater concern due to safely operating the vehicle. In short, the code for Throttle Body, Air Mass Flow Sensor, TPS have all been run, both by me, auto dealers, independent auto shops, and auto electrical specialists. To be very clear, the work has never been handled by any back alley wrenchers. The codes have been run, cleared, run again, disappear for a period of time and then reappear. Frankly, I am worn out by mechanics who are too reliant on the standard run the code, replace the part, bill the owner mentality. A code error for a part can be generated, by a bad connector to a good part. While, I will never claim to be a fully seasoned or professional mechanic, I have done, you name on too many vehicles to count since I was 15 and that includes engine rebuilds. The issue may very well be a short in a particular wiring harness that is intermittent, thus the come and go occurrence of the problem. I am looking for the out of box answers. For the sake of understanding, lets assume, I have run codes, relaced all the above with good OEM parts and the problem still exists, what next?

Next step: We need to know codes.

You may have pin tension issues at the sensor connectors or the module itself. We have made sure the wiring is in goo order and the parts are working correctly then we MUST look at pin tension. This is what an automotive electrical technician would do. L1 certified tech or Electrical tech A6 should find your problem. Ask if you can get an L1 or A6 to look at it. Give them all the info you have and they should give you a time frame for diagnosing. Expect two or three hours.

I have had a couple of reoccurences this morning of the problem and ran codes. Initial fault codes generated with the problem manifesting adn the engine in reduced power mode. were as follows:
P01012
P0171 - Bank 1
P0174 - Bank 2
P0220 - Throttle/Pedal Position Sensor Switch Circuit B
P0650 - Mil central Circuit Open
P1516 - TAC - Throttle Activator Control Module - New Issue
P2135 - Throttle/Pedal Position Sensor - Already replaced

After restarting and depressing Accelerator Pedal 5 times for a reset. Truck started again, and Cleared P0171, P0174, P2135, P0220.

Do you have the timeline for the codes. We need to know which one was first. The codes will have a time since start data line. A good scanner will display it.

Unfortunately, this was a borrowed reader. My scanner stopped working, so I don't have logged error codes to refer back to, to give you a timeline.

I start yanking on things.