UPDATE NO. 2: Replaced accelerator pedal....was not throttle position sensor (engine side of firewall) was actually the accelerator pedal position sensor (cabin side of firewall) seems to have worked

Hooked up
 

Does the onstar need to be activated for it to cause a problem. I get the stabilatrak traction control lights and engine power reduced. But not an activated on star... throttle body has been replaced.

Turned out to be the throttle pedal position sensor. This is actually the throttle pedal assembly (located inside the cab, not on engine side of firewall). I replaced throttle pedal assembly and the problem went away for about a year. It did it one time last month. I am beginning to believe the sensor is just poor quality....I picked up an after market at Autozone

Absolutely no problems after this fix. Thank you.
 

THIS IS THE FIX FOR THE ISSUES OF ENGINE POWER REDUCED, STABILITRAK OFF, TRACTION CONTROL OFF, AND CHECK ENGINE LIGHT ON. I have been troubleshooting for about a year with this problem. Tried several different "fixes" such as marine fuel, throttle position sensor replacement, running seafoam through the tank, fuel injector cleaner, new gas cap, and new throttle body gasket. I gave this a shot for 118$. The next step was going to be buying a throttle body and thats well over 200$. Try this first. Run it through the relearn procedure and see what happens.

Mine did this and I had to replace the throttle position sensor. I also replaced my gas pedal. It would just stall on me and I could turn the engine off, tap the gas pedal and somehow it would reset for awhile until they were both replace.

Likely fix
 

*realized I posted this in the wrong thread directory but keeping here since it may be relevant for folks...*

Hello, I recently experienced a similar issue on my 2009 Cobalt LT after 62,000mi and managed to root cause the issue to a wiring harness problem that affects many GM/Pontiac models.

In short, there is a wiring harness that contains a number of wires that has two really bad chafe points that rub on the oil tank filter under the hood. Over time the harness insulation rubs against the sharp edge of the oil tank filter and eventually can make contact with some of the copper wires. The fix is to wire-tie the wire harness so that it does not rub against the oil tank filter (<$1.00) and a bit of electrical tape around the wire that had insulation cut.

In my particular case, my OBD2 reader was throwing P0641 "Sensor Reference Voltage A Circuit/Open" trouble code. In the wiring schematic, this is known as the "5 Volt Reference (1)" which connects to the fuel tank pressure (FTP) sensor and the accelerator position pedal sensor (APP). Initially, I didn't have time to sit down and play with this so I took it to the shop and my mechanic replaced the entire pedal and APP sensor ($150!) but the issue quickly returned. I would be driving and everything would be find but then all of a sudden I would feel a jerk and the car would lose the ability to accelerate and "ENG PWR REDUCED" and "SERVICE TRACTION" would appear on the display.

The annoying part of this whole thing is that the issue is intermittent and depends entirely upon whether the metal oil tank edge makes contact with the wires. The car was not reliable and my mechanics weren't interested in spending time debugging it. I ended up checking all of the sensors connected to the 5V supply and they were all functioning fine and read 4.8~5V at the sensor.

My breakthrough was when I was fortunate enough to stumble upon the following video below which solved the issue (this fix should honestly be stickied for all GM owners). His symptom was a similar trouble code P0642 "Sensor Reference Voltage B Circuit/Open" but it's the same root issue and the code you will see will depend on which wire in the harness is damaged.

Since the wire-tie fix, the trouble code has completely cleared and I have not had any "ENG PWR REDUCED" or "SERVICE TRACTION" issues for over a month (driving each day).

If the solution works out, definitely help the YouTuber out with likes/subscriptions. I unfortunately didn't see the video before an unnecessary pedal replacement but saved me from selling the car for scraps.

Hope this helps...

JP

2011 Chevy Tahoe LTZ with same issue
 

We live on gravel, and I first experienced this a few weeks ago. If I pull over and turn off the vehicle for a few minutes, when I start it back up it runs just fine. It's starting to happen more frequently. Has anyone had a dealership that will fix it based on these forum suggestions? I even found a YouTube video describing the problem and how to fix.

Malibu LT 2017…. Same issue yesterday. Driving in NYC and the cars check engine came on… freaked me out because it’s so fast paced then I couldn’t go faster than 10 mph. I managed to pull over to the nearest deli **** it off for 10 mins. It was gone. I purchased this car at Chevy and I’m hoping w.e is wrong is covered under warranty. PLUS they lied to me saying I could get a loaner/rental so now I am stuck in mount kisco Ny. After the woman said I might night be able to get a loaner but I could get a rental. So annoyed with this dealership and I Never had issues like this with them before.

i had to replace the throttle sensor cover and so far so good. They also recommended to clean the fuel injectors which I opted to do but the service writer didn’t submit the request.

Chev - Service Traction Control
 

Hopes this helps, got a lot of good help online, so trying to return the favor...
First, this issue is very complex - it could be a number of things. Basically, Chevy designed this error to come up to trigger if any number of things go wrong in your car. Such a bad design... Basically, it is designed to slow your car down if ANY major error occurs (traction loss, power loss, cyclinder issues, electric loss...) which could be triggered by bad plugs, bad plug wires, bad iginition, bad ground connection, electrical issue, traction control issues, ABS issues... the list goes on...
Research this issue online and you'll find tons of posts, tons of issues, tons of advice... Rather than Chevy telling you (or providing an error code for the specific issue - you'll only get the ONE GENERAL error code or issue - Service Traction Control... and sometimes a cyclinder issues. (mine cyclinder #6, #4, then #7...)
Take it to a garage, and they will charge you thousands+ to try to fix this because it is too hard to find, and because they can justify telling you probably need new engine or rebuild, or bad cyclinder/piston... Usually, this is TOTALLY wrong.
OK, here was my fix:
Driving down the road - Service Traction Control light came on, (when this error happens - Chevy design the system to cut back the engine/carb) so my car immediately started driving bad.. bad control, engine cutting back....
Mechanic said it needs new plugs (plug fouled) and plug wires.... $400 - ran ok 3 days - then light came back on
Mechanic said it needed new ignition coil - replaced $750 ran ok 2 days - then light came back on
Mechanic said probably something much serious - will need to go into motor to check piston/cyclinders/fouling.... I said no...
After reading on internet - I tried several of the quick fixes recommended - added new ground wire - no change, replace plugs/wires/ignition coils - incase one was bad - still no change.. new air filter/sensor... nothing, checked batery connections, - took wheels off - checked ABS sensors and connections - looked fine...
THEN - talked to another mechanic he asked what plugs and ignition coil I used - I bought from Advance Auto and bought their premium ones. He said NO they don't work with Tahoes. He cleared all codes, reran truck - read error codes - still pulling error on cyclinder #6 - Service Traction Control light still on...
He replaced ignition coil #6 with a NAPA ignition coil - light went out, no error codes. ($45)
It's been 3 months now and still running fine. I waited awhile because I couldn't believe that was the issue...
Wonder how many other people had this issue, and mechanics charged them thousands to fix....or replaced motor...
Hope this helps.
Thanks Chevy !!!


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