I don't know who needs to hear this, but I spent a month trying to figure out what was wrong with my TPMS system, since the warning lights went on while on a road trip. A month prior, I had installed fresh TPMS sensors on my wheels, and already successfully used my XTool to reprogram the system with the new sensors. Now, diagnostics showed C2126 and read no information at all from the sensors. Just "NA" with no sensor IDs. I attempted to reprogram it multiple times but the reprogramming didn't take, despite getting a "reprogramming successful" message. I also had recently installed a GROM unit, so I thought maybe I had nicked a wire or something when I had the dash apart. I had left the car sitting for a while in wintertime and thus suspected perhaps low voltage on my engine battery was resetting the TPMS ECU. So many possible ways to mess up TPMS.

But it turns out to have been none of that. My kid kicked the switch under the passenger side dash that tells the car I'm using a second set of wheels. I clicked that button again to select the first set of wheels, held the TPMS reset button under the steering wheel for about 10 seconds, turned the car off and on again, and the warning lights went away. All is well again in the kingdom.

So before you go taking your whole car apart to solve for the C2126 code, if it suddenly appears out of nowhere, definitely try clicking the passenger-side TPMS button. (And not only the other "TPMS reset" button under the steering wheel). That is all. Be well.

 

Best thing to do is replace all 5 tpms ! Been there , did all 4 wheels and light still was on . Replaced the spare and bingo! All was good after driving a little bit. All batteries die but not the same time -BETTER OF DOING THE WHOLE SHOW AT ONCE. GOOD LUCK. IF LIGHT STAYS ON POSSIBLE BAD MODULE . BUT BEFORE CHECKING THAT —RECHECK THE NEW ONES MAY HAVE ONE WITH A BAD BATTERY.