TPM Service Warning... a new twist.

[trailerpup]

Have not found this from searching....

I have had my H3 for about 2 months with 3k on the odometer. When I am driving around town I never see the TPM warning all week long... but when I hit the freeway, not less than 5 miles at speed and the "Service TPM" light comes on and stays on. I get into the next town, shut the motor off and fire it back up and drive around, no TPM light. Then back on the freeway, 5 miles at speed and here comes the TPM light. This is like clock work. I wonder what the deal is??? Why would it do it when the tires heat up, and not while driving around. Are my tires filled with too much air and when they heat up the increased pressure is triggering the TPM. I thought "Service TPM" meant there was a bad sensor and "Check pressure" was for a low tire? Remember, my warning say "service TPM." Thanks for any tips!!