you may try a tire relearn. if that doesnt work then when she got her flat it broke the sensor or when the guys put the new tire on they broke it.
To do the tire relearn (3 different ways depending on the model):
06-older:
Set parking brake, turn key to run but do not start, turn headlight knob on and off four times. you will hear the horn honk twice. From there; start at the LF tire and start deflating it. When you hear the horn honk once, stop deflating that tire and move to the RF. Do this to all four tires in a clockwise rotation till you get to the LR, you must start at the LF or the dislpay will show tire pressures for the wrong tires. When you deflate that tire, the horn will honk twice when to stop deflating and the relearn proceedure will be complete. Finally fill your tires to what the sticker on the inside of the door says or to your liking (as long as it does not fall below 32 psi)
07-up base model or limited options:
push the ebrake down and turn the key to run. Depress the little black rod that sticks out of the gauge cluster (will change the odometer display). keep pressing the rod till your odometer screen displays "Hold to perform tire relearn". Once at that screen, hold the rod down till you hear the horn honk twice and the DIC say "tire relearn active". Start at the LF tire and start to deflate untill the horn honks. You will also notice on the NBS tahoes that the marker light for the tire that needs to be deflated will come on (so when you activate the relearn the LF marker light will illumiate, then when the horn honks the RF marker light will illuminate). procced colck wise till you do the LR. Deflate that tire till the horn honks twice and the relearn will be complete. Finally fill your tires to what the sticker on the inside of the door says or to your liking (as long as it does not fall below 32 psi).
07-up high interior upgrade with most or all the bells and whistles:
press the ebrake down and turn the key to run. To the right of the guage bezel you will see 4 little buttons vertically on the dash. Depress the one that looks like a road (should be the bottom one but not quite sure). keep pushing that one till it askes if you would like to preform a tire relearn. Stop there and hold the check mark button till the vehicle honks twice and shows on the DIC "tire relearn active".Start at the LF tire and start to deflate untill the horn honks. You will also notice on the NBS tahoes that the marker light for the tire that needs to be deflated will come on (so when you activate the relearn the LF marker light will illumiate, then when the horn honks the RF marker light will illuminate). procced colck wise till you do the LR. Deflate that tire till the horn honks twice and the relearn will be complete. Finally fill your tires to what the sticker on the inside of the door says or to your liking (as long as it does not fall below 32 psi).
Hope this helps!
