If there is only the one code chances seem to be the ECM is bad. I have had success with a used one preprogrammed to my VIN on eBay for around $100, then you have to pay someone to learn the Crankshaft Position Sensor.

Here is what AllData has to say:

 

I removed the ECM and inspected the pins and the connection harness. There were no recessed or bent pins on the receptacle. There were no frayed or pulled wires from the wiring harness. No one has an ECM in stock, gonna have to wait until Monday to talk to Chevrolet.

How much do you all reckon it would cost to get it looked at by Chevrolet?

Does anyone know what the voltage output should be coming out of the "Starter Enable Relay Control" pin on the ECM going into pin 86 of the crank relay? 1.95V seems pretty low.

*EDIT* Forgot to mention... After reinstalling the ECM, I checked for the error code and its gone now. The car has no error codes but still does not start.

 

As I posted earlier; you can get one preprogrammed to your VIN on eBay. Don't be afraid of eBay?
This for instance:
http://www.ebay.com/itm/2008-Chevy-M...ZUJC9B&vxp=mtr

 

Is not that I am weary of Ebay, it's the fact that I do not live here and I would have to keep driving here to fix the vehicle. At this point, we're considering having a mechanic fix it depending on the cost. I don't want to go through the trouble of getting one from e-bay to only find out it is a wiring issue.

 

The one I got last year was money back, no questions, pay return shipping. It cost $12 to ship it back.

If you get a new one it will need programming by someone with access to TisWeb and then have the Crank Sensor learned. Used ones run about $25, new run $75-$300. A dealer may no want to work with a used one.

 

I suspect the ECM and TCM ground, which meet on the transmission just below the oil filter then grounds to the upper radiator support driver side

Since you seem stuck on the starter system, here is a schematic:

 

Thanks for the schematic. I'm thinking of taking your suggestion and ordering one of eBay. Once I get it, won't I still have to take into the mechanic to program the ECM?

 

They will do the firmware part. They will tell you to do the anti-theft reprogram (no need, different system in HHR). The CranKshaftPosition sensor will either need to be learned or some of the vendors will delete that requirement from the firmware (bad idea).

The motor will run plug n' play, but you will have a CEL for P0315 until the CKP is learned.

Be absolutely sure to check all of the underhood and dashboard ground locations. If any of the "computer" modules has lost power the U0100 will be triggered. A mechanic that was awake the day they discussed the CAN Bus in the class room (not easy to do) should be able to diagnose which module is not right.
Check this link out:
https://www.chevyhhr.net/forums/how-...can-bus-56781/

 

Just wanted to give one last final update.

I finally got around to replacing the car's ECM. This finally fixed the issue. Thanks everyone for your input in helping me solve this problem, especially donbrew.

 

Glad I could help.