RepairPal Certified shops can diagnose and repair your 2007 Chevrolet HHR. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
I had the same problem. I replaced the thermostat and that fixed the problem. The new thermostat will remain open when they mess up. Mine also said coolant temp low. Hope this helps.
Thx Goodguy, Where is the sensor located?