[Advent327]

this answer the question...

Block heater on GM vehicles
GM has installed temperature sensing circuitry into the plug on factory installed block heaters. It prevents the heater from operating unless it is colder than 0°F or -18C. It may seem insane, but it really does make sense if you understand why. If you install an aftermarket block heater without this circuitry, the PCM will see warm coolant, but a cold engine and cold air coming into it. Remember, it's the PCM's job to determine the correct air/fuel mixture. A cold engine block and cylinder head act as a fire extinguisher when you first start up the engine. So the computer commands a very rich mixture. How does it know what temperature the engine is? It used to look at only the coolant temperature. But now it looks at both coolant temp and the temp of the metal itself. If it see a discrepancy between the two numbers, and the outside air temp coming in through the intake is 0° or above, it assumes there's something wrong with the coolant temp sensor and sets a trouble code.

Bottom line, if you add an aftermarket heater, it must have the temperature sensing circuitry in it or you WILL set a trouble code. Also, if you ever have to replace the power cord to the factory block heater, you must use a new GM power cable

2015 Traverse (Posting 25/2/21) Canada - Prairies - I know cold !.
Super helpful. Cord is splinting near the plug end that has built in sensor. Was going to simply replace with new male end..not now. Not sure I fully understand the WHY, but if there is a chance that codes are going to show-up, no thanks. Will I buy a new GM cord ? probably not...they are $100+ and if they only trigger colder than -18c, whats the point. Even on the prairies we see colder than -30 at times in the winter, but I think I'll throw in a new battery and run with it. This is a 6 year old car with 116Kms.. Thanks

 

[Advent327]

I got my cord from partsavatar for $36.48+tax. They put a thermostatic there for a reason. If your car won't start at -18C then you should plug it in and ensure your battery is fully charged.

Hmm . Ok thanks for parts info. Much appreciated. That does change things. I have my car in GM today for a list of things...I’ll let you know on their quote to replace. Love having that knowledge in my back pocket. Much appreciated.