Tire pressure monitoring system or tire problem making system?
Greg Horn
Technology has immersed itself in every facet of today's vehicles. The National Highway Traffic Safety Administration (NHTSA) requires automakers to include technology like the tire pressure monitoring system (TPMS) in vehicles, with a phase-in period from 2006 to 2008 on light passenger vehicles. This sounds good for consumers, but what does it mean for the collision repair industry?
A TPMS monitors air pressure inside pneumatic tires on various types of vehicles and reports the tire pressure information to the driver. There are two basic types of TPMS – direct and indirect.
- Cope with temperature changes that influence tire pressure. Pressure ranges that trigger warnings are usually taken from the manufacturer's recommended cold inflation pressures.
- Employ actual pressure sensors inside each tire and a means of accumulating and transmitting that information to a vehicle's central computer.
- Use a radio frequency communication channel to transfer the data from a rotating wheel.
- Recognize under-inflation simultaneously in all four tires in any combination.
- Compare individual wheel rotational speeds provided by the vehicle's ABS to detect an under-inflated tire due to its marginally higher rotation speed.
- Do not use actual pressure sensors and are lower cost.
- Attractive to vehicle manufactures because of lower cost combined with the federally mandated ABS requirement for all ESC cars sold in the United States in the 2012 model year.
- Accuracy of this lower cost system has been questioned by several studies.
Over- or under-inflated tires can be a safety issue because they make vehicles harder to control in evasive maneuvers, such as sudden sharp turns or lane changes. Underinflated tires also waste gas and cause tires to wear prematurely. A recent NHTSA study shows that 57 percent of vehicles in the TPMS equipped control group had correct tire pressure, with the non-TPMS equipped control group at 43 percent.
For collision repairers, the relative fragility of the actual valve stem/monitor can be a major issue. Many OEMs supply a one-piece valve stem monitor that can leak and need to be replaced if it is inadvertently knocked around during a repair. Many TPMS valve stem monitors are VIN specific and may require special order, with an individual valve potentially costing about $85 or more — plus the time it takes to remove and re-mount the tire.
If a leak or TPMS warning light goes off just prior to vehicle delivery, you will scramble to have your sublet tire partner obtain and install the replacement part. Additionally, insurance adjusters may be hesitant to pay for a TPMS when they feel that no direct impact to the part is evident.
The impact of a bad sensor may be most felt on your CSI score. Let's say for example your technicians are washing a car for delivery and notice that the TPMS warning light is on. They may simply fill the tires until they see the light go off. The vehicle owner takes the car home and the next day, the warning light goes on because there is a slow leak. The owner may automatically assume that something occurred during the repair, likely resulting in a customer who is no longer completely satisfied.
It is well worthwhile to check the system for proper operation upon vehicle intake and make the owner aware if the warning light is on. The owner may let you know that there are many false warnings with the system or it's been on since the accident, in which case you can add that to your appraisal. However, if the light goes off prior to delivery and the system was working properly at intake, a quick leak diagnosis is time well spent to keep your customer satisfied.
As more cars enter the vehicle population with TPMS systems – everyone from shop owners to technicians and estimators – must educate themselves on the technology to establish vehicle intake and delivery procedures that adequately address TPMS-equipped vehicles. Underinflated tires can affect your customer's satisfaction with the repair, so it's not a time to be penny wise and footpound foolish.
Greg Horn is vice president of industry relations for Mitchell International.
