How to put 2021 Yukon into "run" position?

[jasonpblair]

So my wife had just put the Yukon into drive, noticed a guy pulling out of the parking lot way too fast, so she put the Yukon in reverse almost immediately. Apparently the TCU didn't like the quick button press from Drive to Reverse, so it went into limp mode. She had to shut the car off and turn it back on, and now it runs and drives normally.... Except the check engine light is on with an 0700 Transmission code. I'm trying to clear the code with my OBD2 scanner, but it says to put the car into "run" with the engine off. I do this all the time with my other vehicles, but I can't figure out how to put the Yukon in "run" with the engine off! When I try to clear the code with the engine running, it says it cannot clear the codes while the engine is running. When I shut the engine off, the scanner says that it cannot communicate with the ECU while the vehicle is off, and it tells me to turn the ignition to the "run" position.

Can anyone help? How do I get the Yukon into "run" without the engine running? (2021 Yukon XL Denali, 3.0 Duramax.)

Thanks!

 

[Chad G 1979]

I believe run mode on these vehicles is pressing the start button WITHOUT pressing brake pedal.

 

[jasonpblair]

Thanks, I tried that. Didn't seem to work. Anytime the engine isn't running, the OBD2 scanner says "Error communicating! Please turn ignition to RUN position with engine OFF." It seems more like pressing start without pressing the brake pedal is more akin to putting a can in "Accessories" mode than "run" mode. My wife's Wrangler also has push button start, but if you don't press the brake pedal, there are lights that scroll through "OFF - ACC - RUN." No dice on the Yukon.

(In other news, the check engine light on the transmission code eventually just went out on its own this afternoon... But I'd still like to figure out how to clear codes without taking it to the dealership for future reference.)

 

[972sparky]

Push the start button without brakes applied for 5 or more seconds to put into service mode. Push again to turn off when done with your diagnostics.

 

[StephenPT]

Push the start button without brakes applied for 5 or more seconds to put into service mode. Push again to turn off when done with your diagnostics.

This is the part the OP was missing - pushing the button without the brake applied puts you into "ACC" mode. Press and hold for 5 seconds puts you into "RUN" mode.