Bulletin 07-03-16-004 was just released to provide additional information about the Tire Pressure Monitor System (TPM) that is standard equipment on all 2008 US vehicles (except Saturn Astra) and optional on some vehicles in previous model years.

Here are some highlights. See the bulletin for complete details.

Before performing service on a TPM system, it's important to distinguish between the two instrument panel messages related to TPM operation.

A Check Tire Pressure/Low Tire Pressure message indicates that tire pressure needs to be corrected and that the TPM system is operating as designed. This does not indicate a need for diagnosis and correction, other than correctly inflating the tires.

A Service Tire Monitor message indicates that there is a condition that should be diagnosed and corrected. System codes will set.

The bulletin explains the effect of outside temperature on tire pressure. Typically, tire pressure changes 7 kPa (1 psi) for every 6° C (10° F). Pressure drops as temperature drops. A Check Tire Pressure message is displayed if tire pressure is at 75% of the recommended pressure.

A drop of a few degrees of temperature may be sufficient to cause the message to display. As the tires warm up, the message may turn off. This is normal operation and does not call for repair, other than correctly inflating the tires.

The bulletin includes tips on using the TPM Tester J 46079.

The bulletin also includes an extensive FAQ section, which may be shared with a customer to further assist them in understanding the operation of the TPM system, to avoid unnecessary customer concerns.