I keep getting a warning on my DIC for my 2007 TrailBlazer telling me to service the tire monitor. This happens when one or more TPMS sensors lose signal with the system. You can determine which TPMS sensor is failing by scrolling through the DIC after receiving the message. Go to Tire Pressure and you will see "---" for one or more tire pressures on the DIC. This is because the battery in the sensor is dead. Unfortunately, due to NHTSA and DOT regulations, the sensor is designed in such a way that the battery is not replaceable, but the entire sensor is replaceable. The battery used is said to have a lifespan of 10 years, but I only lasted about 8 years with mine. Also, it's best to replace all (4) TPMS sensors at once, especially as they approach the 10 year mark. There are several GM-specific TPMS sensors, but you can determine which TPMS sensor you need by looking at your RPO code list, which can usually be found on the nameplate in the glove box. If you have RPO code "UJ6" then this sensor will work on your GM vehicle. Also be sure to purchase a new ACDelco Sensor Lock Nut 15234846. You can probably reuse the old locknuts, but in many cases they will corrode or become damaged when removed. The lock nut is only $6 each.