My understanding is that the mode will not deactivate the use of buttons on the key fob, but rather the passive entry feature that allows you to unlock the doors by pressing the button on the door handle. It also deactivates other things like the theft alarm. And these changes don't take effect right away, but after a timeout period which I think is 1 day or so since the car was last turned on. So that makes it a little hard to test.

It is smart to use transport mode for your situation. The manual advises keeping it plugged in if possible.

 

The passive lock/unlock(door handle buttons) worked fine in Transport mode. You could be right about the timeout period.

 

This is an excerpt from the Owner's Manual regarding Vehicle Storage....

Up to four weeks
. Plug in the high voltage battery
charge cord if temperatures will
exceed 35°C (95°F) and keep
the 12-volt battery cables
connected.
Four weeks to 12 months
. Discharge the high voltage
battery until two or three bars
remain on the battery range
indicator (Battery symbol) on the
instrument cluster.
. Do not plug in the high voltage
battery charge cord.

For short-term storage, the 12V coolant pump apparently comes into play if the HV battery that's fully charged gets too hot. If the coolant pump was running too much, however, this could drain the 12V battery unless design provisions are made for recharging it.

As for long-term storage, the HV battery apparently won't overheat (even in high-temp ambient conditions) because of the low state-of-charge (SOC).

In either case, I think that the Transport mode is something to consider.

 

I don't believe that the 12V battery, by itself, will run the coolant pump and/or the radiator fan if the Volt is powered off. If the Volt actually does cool the battery pack when the Volt is not plugged in (I am not fully convinced that this happens) then the high temperature conditions for this to happen would require the AC to run to cool the battery pack. So the Volt would turn on, as if it was preconditioning, run the AC, the coolant pump and the radiator fan all while drawing power from the traction battery pack to power the high voltage AC compressor and also powering the 12V components via the accessory power module (APM.)

 

9/17/19 Update - After being in Transport mode for several days, it started working as advertised. Passive and key fob lock/unlock was disabled. Unfortunately, the fob key would not unlock the car! Tried two different keys with same result. I don't remember ever using the key but entertained the idea that the Transport mode may have screwed things up. Fortunately, there was still two months of Onstar left and the automated (phone) unlock system worked. I quickly disabled Transport mode and promised myself that I would never use it again.

The car was left unattended (and unplugged) for two weeks with 22 miles SOC. Wasn't concerned about high-ambient temps since the traction battery wasn't fully charged. If the 12v battery ever dies, I'll be in a real jam since the key won't unlock the car. May have to break down and have the key lock/unlock system repaired.

 

Thanks for the update. Why won't your keys open your door? Do you have replacement key fobs that were not cut for your car, or maybe a replacement lock cylinder (or replacement door) not matched to your original keys?

If you have the wrong keys, I think it is possible to have new ones cut at a dealership based on presenting them with your VIN and proof of ownership, in case you get locked out with a dead battery. This only works if you have the original lock cylinder.

 

Original lock and key fobs.... nothing changed.

 

So have you tried to physically use the key (not the fob) to manually stick it in the keyhole to open up the door? I think that's what Barry is asking.

 

Yes, I have tried to physically use the key by inserting it in the keyhole. Same result using both keys.

 

I wonder if this varies with Volt model year. I have a 2018 and the steps to activate Transport Mode are slightly different. And yes, the key fob still works.

But - the end result is the same -- no draining of the battery. Tried this about 2 weeks ago when leaving my car in a garage, in-plugged. Charge was fine after a whole week. I don't know if one week is long enough, but the key fob thing is different from the original instruction post.

 

I'm not sure if you're getting what Transport Mode is for which is to emulate "disconnect the 12 volt battery" (by putting the car into a low power deep sleep mode instead of the normal sleep that happens after three days of no operation) in a way that's reversible without having to get out a wrench. The traction battery will be fine either way. It gets disconnected from the car every time the car is turned off.

 

5/21/2021 Update - As previously discussed, after enabling Transport Mode and then disabling it several days later, the physical key in the fob would not unlock the car. I knew that I would be in trouble if the 12V battery died. Not being able to get in the car to pop the hood, a jump start was out of the question.

Knowing that the original 12V battery was almost seven years old, I was getting increasingly concerned. I was quite certain that the physical key was able to unlock the car at one time and that the Transport Mode might have screwed things up. At this point, I decided to disconnect the negative lead of the 12V battery and reconnect it after ten minutes, hoping that it would reset the system after rebooting. I'm happy to report that doing this solved the problem. I will never, ever use Transport Mode again for any reason!