I have a 2003 CTS with 48,000 miles. MIL came on and dealer said I need a new thermostate after they hooked up to computer. After 5 days my engine light went out. Do I still need new thermostat? Car not over-heating. Thanks.
Possibly. It could be sticking and starting on a downward spiral or a misread in codes.
With potential overheating problems I would err on the side of caution rather than face sitting on the side of the road waiting for a tow truck. Overheating most modern engines typically means very expensive engine repairs.
I had a thermostat that opened prematurely and made the engine run too cold. ( This can set the MIL light on). If it is the original thermostat, you are due for a new one anyway.
A thermostat is relatively cheap, even for a CTS. I don’t know why you didn’t get one when you were at the dealership, or why you continued to drive with your MIL still burning. Not a good idea.
You may be able to drive for quite some time before this incident recurs but I suggest you take care of it now. And it need not be at the dealership. Anyone can replace your thermostat, and most likely do it for much less.
Adding to what has been said, you don’t want to mess around with a failing thermostat. The light went out, things seem fine, then before you know it, Summer rolls around, it’s a 95 degree day, the thermostat sticks closed, and you’re getting towed to the dealer for a $4000+ engine problem.
I think you are refering to the CTS sensor and not the thermostat. The sensor is there for the ECU to read the coolant temperature and is different than the sensor for the dash gauge, which will not send a error code like the CTS sensor will if there is a problem with it or the circuit to it. Since the problem has cleared I suspect what really happened is the connection to the sensor is just dirty and needs to be cleaned up. I may be wrong though, but I would check it out.