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Originally Posted by f5fstop
Gray area? Ok, from what I know (and who knows it might be incorrect), but on the H3, the BCM does not read each corner, but each sensor, not knowing which corner it is located at. Which goes along with the fact that on an H3, if you rotate the four tires on the ground (no spare), you do not have to reset (reprogram) the sensors. The BCM still sees the same four recognized sensors, so it is happy.
However, if you mix in the spare, it now sees a new sensor, and does not see a known sensor, so you have to reset the sensors to be recognized by the BCM.
On those vehicles such as Caddys that do read each corner separately, and display the tire pressures for each tire separately in the DIC, when you rotate the tires, you have to reset the system, so the BCM knows the front right sensor is now at the rear left wheel location.
Now, possibly, inside the BCM there is a chip that is looking at each sensor as it was programmed, and if you don't reprogram after a rotation, it will be confused, but not know any difference since you don't do the reset. However, I have failed to see this on the GM Tech 2 scan tool, and usually, what Onstar is picking up is what can be read on the Tech 2. (Maybe I need to go back out and do some more digging on the Tech 2.)
So, if the BCM can determine which sensor is at which corner of the vehicle, then when you rotate the four on the ground, even though the TPM message stating a system problem is not displayed, you would have to reset the sensors to that particular corner of the vehicle.
However, as Viet Nam Vette implies, 30 days is too long to not check your pressures, even if a TPM message is not displayed.
I will be curious, but will not know unless someone informs me on the forum, since I canceled the worthless (my opinion) Onstar service, and told them to shove it up to where the sun does not shine.
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