SOURCE: 2006 HHR, check engine light came on, the engine Your coolant temp sensor is not registering. It probably set a trouble code, that's why your remote vehicle start is not working. The temp sensor is located at the rear corner of the engine block on the back side of the engine.
If you, in fact, have low coolant level, this is what is supposed to happen: needle stuck at the left hand side and the warning light flashing. Check with the dealer and don't run the engine until you know for sure.