Did you know this about TPMS??

[Thai]

"Tire-Pressure Monitoring Rule: NHTSA issued a rule that requires all vehicles weighing 10,000 pounds or less to have tire-pressure monitoring systems (TPMS) by model year 2008. Vehicle manufacturers will be required to install a system that can detect when one or more of the vehicle's tires are 25% or more below the recommended inflation pressure. The new safety standard, Federal Motor Vehicle Safety Standard No. 138, will be phased in starting in September 2005. Twenty percent of MY 2006 cars will be required to comply with the rule, increasing to 70% of MY 2007 cars, followed by 100% of all MY 2008 cars. While the rule is technology neutral, NHTSA estimates that the new systems will cost between $48 and $70 per vehicle using systems currently in the marketplace. Although the TPMS does not have to operate after the vehicle has been sold and replacement tires/wheels are being installed, NHTSA believes mechanics should have enough information to keep the TPMS operational or install substitute TPMS equipment. Nevertheless, it will be illegal for a tire installer or repair shop to disable the TPMS malfunction light on the dashboard."

No wonder more and more cars have TPMS.

 

[toto]

Toyota was well ahead of that mandate. If you read that literally, it allows for the "passive" TPMS which uses the ABS computer to compute wheel speed; if one tire is lower than the others by several pounds, that will detect it. The safety advocates that got the TPMS mandated were screaming about that loophole, as passive TPMS has several flaws. For example, if they're all too low, it won't know that, and that was a key problem in the Ford Explorer/Firestone fiasco. However, passive style is much cheaper and simpler than active TPMS, which puts sensors in each wheel.

Toyota tried the passive TPMS and lived the nightmares of the shortcomings. They even had to issue a TSB for the 2004-05 Lexus RX330 because the computer was completely wrong under certain driving conditions. All they could do there is change the software, but you'll notice that Toyota isn't using passive TPMS any more.

Toyota's active system isn't as nice as some others, IMO. Honda's can tell you which tire is the problem. Toyota's design registers ID's of all 5 wheels, but it has no clue which wheel is in which position. In contrast, Honda's system figures that out. I imagine they're doing that with multiple receiver radios, essentially triangulating the position of each wheel sensor. You don't tell the computer when you rotate tires, so that's not something you have to configure. Honda then has a small picture of the car on the dash, and the low tire lights up.

 

[rook]

Toyota's active system isn't as nice as some others, IMO. Honda's can tell you which tire is the problem. Toyota's design registers ID's of all 5 wheels, but it has no clue which wheel is in which position. In contrast, Honda's system figures that out. I imagine they're doing that with multiple receiver radios, essentially triangulating the position of each wheel sensor. You don't tell the computer when you rotate tires, so that's not something you have to configure. Honda then has a small picture of the car on the dash, and the low tire lights up.

Toyota would merely need to update the software. Each sensor has a unique id. This is what is programmed ino the tpms unit. By updating the software, and assigning a specific sensor to a specific position, this system can tell you which tire is low. Toyota may have omitted this feature, because it would require reprogramming at every tire rotation, increasing ownership costs.

Originally posted by thai

Although the TPMS does not have to operate after the vehicle has been sold and replacement tires/wheels are being installed, NHTSA believes mechanics should have enough information to keep the TPMS operational or install substitute TPMS equipment. Nevertheless, it will be illegal for a tire installer or repair shop to disable the TPMS malfunction light on the dashboard."

Good to know for those of us who run a 2nd set of wheels/tires in the winter.