Programming Keys, 2012 Sierra HD

C/K Man · November 27, 2022

Is it possible to program a key to work in 2 different trucks (both 2012 Sierra HD's)? Key is cut the same. I have been told that once a key is programmed to a particular vehicle it won't work in any other vehicle. Can't find that mentioned in the service manual.

davester · November 28, 2022

That sounds like a "you'll have to try it and see" kind of thing.

You could try it out relatively cheaply, assuming you have the two trucks already), by making a new key for one truck, but using a plain key (instead of one with a chip). Then go through the process for adding a key to the truck you made the blank for, but holding a key programmed for the other truck up to the ignition switch while inserting/turning the blank key. Then see if it works with both vehicles (one normally, the other by holding it to the ignition while using the blank).

C/K Man · November 28, 2022

Good idea.

newdude · November 28, 2022

16 hours ago, C/K Man said:

Is it possible to program a key to work in 2 different trucks (both 2012 Sierra HD's)? Key is cut the same. I have been told that once a key is programmed to a particular vehicle it won't work in any other vehicle. Can't find that mentioned in the service manual.

Are you sure the cut is the same? Did you install a new cylinder that has the same cut as the other truck?

C/K Man · November 28, 2022

3 hours ago, newdude said:

Are you sure the cut is the same? Did you install a new cylinder that has the same cut as the other truck?

That is the plan, a new key and cylinder cut the same as the other truck.

swathdiver · November 28, 2022

Shouldn't be a problem, the trucks don't talk to each other and the keys don't either.

newdude · November 28, 2022

On 11/28/2022 at 1:30 PM, C/K Man said:

That is the plan, a new key and cylinder cut the same as the other truck.

Gotcha.

So the best route to do this would be put the new cylinder in that will be built to the same cut as the other truck, and then attempt the 30 minute key learn with the key from the other truck. That should program the other key to the other truck's system and would erase any existing programmed keys.

With these older trucks, the theft system learns the transponder value of the key to the theft deterrent module, rather than the key learns the truck. The new stuff with push button or the flip igntion keys, etc. they have the ability to store the VIN of the car and can't be programmed to more than one vehicle.

The 30 minute procedure is on the last two pages here - GM Vehicle Theft Deterrent Relearn Procedures.PDF (jetchip.com)

EDIT: May or may not work as I mis-spoke on the key having a resistor, rather, passkey III uses a transponder in the key.

Edited November 29, 2022 by newdude

davester · November 29, 2022

2012 doesn't use a resistor, it has some kind of chip in the key. That's why I suggested doing that test, as IDK what kind of data is passed between the theft deterrent module and the chip in the key as part of it's authentication process.

newdude · November 29, 2022

9 hours ago, davester said:

2012 doesn't use a resistor, it has some kind of chip in the key. That's why I suggested doing that test, as IDK what kind of data is passed between the theft deterrent module and the chip in the key as part of it's authentication process.

Correct, I mis-spoke on that. I wonder then if the transponder in the key learns the vehicle? That I know of and how the operation of it seems, its the theft deterrent module in the truck that picks up the value of the key.

C/K Man · November 29, 2022

2012 uses Passlock III. The key does have a transponder activated by the immobilizer module in the steering column when starting.

Edited November 29, 2022 by C/K Man

C/K Man · December 2, 2022

This is getting interesting. We have a truck (theft recovery) and changed the door and ignition locks, keyed the same as another truck (same year) we have. Reprogrammed the Passlock, key works fine. Tried to add that key to the other truck with the same key cut, truck did start but display says 'Passlock Fault'. Starts once but will not restart. Going to scan it and see what the code is.