My HHR was showing all 3 intemittently, they would come on and then be off the next time I started the car. The problem ended up being the MAF/AIT sensor that is mounted in the air intake hose just before the trottle body. This can be replaced in 5 minutes with the correct Torx head screwdriver. Be sure to buy the AC/Delco replancement, NOT a Dorman, or the problem will come back in just a few thousand miles. I should know, I learned the hard way!
I did run a scan before replacing the sensor, it revealed the problem.

 

Thanks for the information, enjoy the ride!

 

How did your scan reveal the problem was the MAF? The codes you cite would not indicate that, the MAF/IAT has its own codes and sometimes cause other codes.
Not arguing, just looking for details. The times I had a bad MAF I did not have misfire codes.

 

I expect the traction control to come back. It has no relationship with the MAF/IAT.

 

BTW; whatever your reader might rsay P0300 does not mean " random misfire" it does mean "unidentified misfire"". It generally has to do with timing not always.

 

I replaced the OEM MAF/IAT unit when I got these codes 6,000 miles ago. The 1st Dorman replacement worked 4,000 miles before the same codes came up, the second lasted 2,500. Then I installed an AC/Delco unit, the quality is different if you hold them side by side. No MIL so far.
I was not in on programming the ECM the GM installed in this car, and I didn't design the MAF sensor, but understand its function. I cannot explain why these codes appear, but they must be tied together somehow in the programming. This is a question for an engineer.

 

The traction control MIL hasn't come back. The ECM may take out the traction control under various conditions is the best I can figure, in the interests of driver safety and control. Just a guess, I did not design the system.
NOTE- low brake fluid or a faulty brake fluid level sensor can trigger a traction control MIL in some GM cars. The fluid level and sensor are good.

 

A note to all of you who are quick to question my intelligence or pick apart my post, I am only the messenger who is sharing my experience with you. Take it as that, there's no need to go further. I told you what worked in my car, take it or leave it like OldBlue did.

 

Amen!

 

Did somebody "question my intelligence or pick apart my post"? That must have been deleted.
It is a very well known fact around here that most "engine sensor" codes will cause the traction control to turn off. #1 to alert the driver that ignores the pretty lights on the dashboard and #2 Why do you need it if the car is not functioning properly and should be parked. #3 because the computer goes into open loop mode. Most of the faults are not perceptible to the casual driver so the computer throws thing at the driver like turning things off and making hard shifts.