This notice of proposed rulemaking (NPRM) proposes to establish a new Federal motor vehicle safety standard mandating tire pressure monitoring systems capable of detecting when a tire is significantly under-inflated. A prior version of the standard, adopted by the agency in June 2002 in response to a mandate in the Transportation Recall Enhancement, Accountability and Documentation Act, was vacated by a decision issued by the U.S. Court of Appeals for the Second Circuit in August 2003. This NPRM, which is consistent with the Court's decision, proposes to require installation in new light vehicles of a tire pressure monitoring system capable of four-tire, 25-percent under-inflation detection. This proposed rule differs from the final rule also in that it tentatively responds to issues raised in petitions for reconsideration of the June 2002 final rule and proposes to require a TPMS malfunction indicator.

The ruling by the U.S. National Highway Traffic Safety Administration currently only applies in the U.S. But Canadian vehicles are generally outfitted to U.S. specifications, so you'll see TPMS here.Since Transport Canada works closely with NHTSA, there's a good chance it will become law in Canada as well.
The mandate resulted from congressional hearings on Firestone tires, says NHTSA spokesperson Rae Tyson. Underinflated tires were partially blamed for several rollover crashes involving Firestone-outfitted Ford Explorers; the crashes led to a voluntary recall of 6.3 million tires, starting in 2000.

The introduction of tire pressure monitoring system tell-tales and an indicator

On April 8, 2005, the U.S. Department of Transportation published a Final Rule establishing a new Federal Motor Vehicle Safety Standard, No. 138, which mandates that all vehicles with a GVWR of 4 536 kg or less be equipped with a tire pressure monitoring system (TPMS) in order to warn drivers when the pressure in one or more tires falls below a specified level of inflation. (see footnote 10) Among other things, FMVSS No. 138, "Tire Pressure Monitoring Systems," introduces a requirement for either of two designated low tire pressure warning tell-tales to be installed inside the occupant compartment in front and in clear view of the driver. The Standard also mandates the installation of a TPMS malfunction tell-tale that must signal when the system is not operating properly. The malfunction tell-tale may consist of a separate, dedicated indicator to be identified by the letters "TPMS," or it may be combined in the specified manner with the low tire pressure warning tell-tale selected by the manufacturer. The two permissible symbols to be used for the low tire pressure warning tell-tales, as well as the mandated abbreviation for the TPMS malfunction tell-tale, all three of which must be yellow in colour, have been added to FMVSS No. 101, "Controls and Displays." (see footnote 11)
Although Canada does not intend to require vehicles to be equipped with a tire pressure monitoring system for the moment, this amendment proposes to add the two low tire pressure warning tell-tales and the malfunction tell-tale for vehicles equipped with a TPMS to section 101 of the MVSR. The adoption of these tell-tales, which would have to be yellow, would ensure uniformity between the symbols used in the TPMS-equipped vehicles sold in Canada and the United States.