2008 tire monitor

how do the tp monitors work I have one that is showing no pressure but its allright. how do you diagnose the problem?
thanks you
PS anybody have a pdf of service manual for that year?

http://www.chevrolet.com/content/dam/Chevrolet/northamerica/usa/nscwebsite/en/Home/Ownership/Manuals%20and%20Videos/02_pdf/2008_chevrolet_hhr_lt_owners.pdf

This is a PDF of the owner's manual......starting on page 5-61, it explains the TPMS.....


If the the pressure is ok in the tire, the tires are in the correct positions, and this just happened out of the blue(you were not trying to relearn positions), then chances are your tire sensor/battery has gone bad........

http://www.chevrolet.com/content/dam/Chevrolet/northamerica/usa/nscwebsite/en/Home/Ownership/Manuals%20and%20Videos/02_pdf/2008_chevrolet_hhr_lt_owners.pdf

This is a PDF of the owner's manual......starting on page 5-61, it explains the TPMS.....


If the the pressure is ok in the tire, the tires are in the correct positions, and this just happened out of the blue(you were not trying to relearn positions), then chances are your tire sensor/battery has gone bad........
only does it when the temp is near 100 deg

Found this:

When asked how long the sensor batteries will last, industry representatives provide a broad life expectancy range of five to seven years and up to 100,000 miles are mentioned when addressing estimated life spans. The follow-up qualifier is that driving conditions, such as frequent on-off cycling of a TPMS, tire pressure sampling frequency and temperature extremes, will significantly shorten battery life. Translating to they cannot guarantee a specified amount as many things affect battery sensor life.

For now, though, the batteries are generally round and encased in a sensors molded plastic housing have finite lives. Since the batteries are entombed, a dead or dying one requires the replacement of its entire sensor assembly.