Flashing a tune accessory or service mode?

[Tyebo185]

Getting ready to tune my 17 Yukon. This is the first vehicle I’ve put a tune in with a push button start. Should I put the truck in accessory mode or service mode for the flash? Just don’t want the power to cut off in the middle of a flash. What has everyone else done? Thx.

 

[BlackBearPerf]

Typically, you'll need to press the Acc (Accessory) button with your foot off of the brake pedal.

 

[BlaineBug]

Even so, accessory mode times out after so much time. Requires pressing and holding the start button with FOOT OFF BRAKE for a considerable amount of time before it wakes up, not just a quick press like with other makes/models.

 

[THarber]

The tune I installed inmine required several cycels of on/off acc. Not sure what yours requires but I never had a problem of mine timing out at all.