Originally Posted by Airbag

in simple terms - the CTS is one of the highest failing parts of our cars , and yet one of the cheapest to replace . i would consider it a maintanance item for every 5 years just to keep it from annoying me.

The CTS will monitor the coolant temp .. it richens the mixture when the car is cold and leans it out as the senses the coolant warm up . depending how it goes bad it can dump fuel in constantly thinking the car is cold. therefore bad fuel consumption and cooked cats.