My 09 Chevy HHR recently started showing 'Service Traction Control' and 'Reduce Engine Power' and power is reduced .Car starts sputtering.

Any dtcs set?

P2135 when scanned

Throttle positions 1 and 2 do not agree at times inside the throttle body assembly. Gm does have a bulletin out to inspect the wire harness for chaffing near the transmission bell housing and checking the ground circuits and to recrimp the ecm terminal connections.
Id check for loose terminals at the throttle body connector. Apply some electrical grease to the connector. A lot of times its a terminal issue, Gm used the weakest terminals on our drive by wire systems. If you have a Dvom you can check and verify your circuits check ok.

I took my 09 hhr to dealership I purchased it from. Their gm certified technician said I needed a new throttle body. Since i dont have a warranty I replaced the part and took to them to program. Before I got home it started doing the same thing. I have only had this car for 5 months and getting very frustrated. I would appreciate any advice ....

90% percent of the time its a terminal fretting issue or loose crimp at the terminal. Did they mention anything about checking the engine control module connections at the connectors? I cant stress enough on how many times a simple recrimp of the terminal will fix this. It doesn't take much resistance to throw this system off.

Unfortunately, have seen wiring problems cause unnecessary replacement of hard parts.......have seen transmissions put in needlessly, because of a broken wire inside the insulation......

There are too many techs out there, that look for the quick fix, and lack diagnostic intelligence....they are called parts changers....

I hold GM techs to a much higher standard, than other techs, when it comes to working on GM cars....these guys have the training available, the tools available, and a backup system of technical assistance, to fix it right the first time.....there is no excuse, for a customer to pick up his vehicle, from a GM shop, and find the problem has not been fixed......I can see that happening when GM vehicles are repaired at non GM shops.....too many times those techs use diagnostic services, that give probable solutions to problems without diagnosis...and you can't blame them for that....they may not have access to wiring diagrams or trouble trees, and basically are parts changers.....I am not saying that all non GM techs are like that....there are quite a few non GM techs, that know more about GM cars, than GM techs.....because they take the time to learn.... but You can understand this happening, if they don't have the proper training, special tools, and support system....

I've always said, need tires, battery, exhaust, or brake work done? Can go to just about any shop.....but if you have driveability problems, go to a dealership.....and when you go there and talk to the SM, you ask him who his best diagnostic guy is, and ask that only he works on your vehicle....and if he doesn't fix it, you rip that SM a new one.....

"I took my 09 hhr to dealership I purchased it from. Their gm certified technician said I needed a new throttle body. Since i dont have a warranty I replaced the part and took to them to program. Before I got home it started doing the same thing."

Was this a question he answered, or did he actually diagnose the vehicle and charge you for his diagnostic time?

So they programmed the vehicle? Does the repair order say they road tested the car? Or was the shop just told to program the car?

I hate it when two or more parties are doing a fix on the vehicle, because who do you blame when these situations crop up?