Since 2008 when TPMS (tire pressure monitoring system) became mandatory on all U.S.-sold passenger vehicles, the need to have them serviced has changed the tire market. The idea behind the system is simple: monitor each tire for an air pressure loss greater than 25 percent (or about 5 psi) and send a visual warning to the driver of the low pressure. But, that’s where the simplicity ends.
One of the significant safety advantages of monitoring tire pressure is to prevent underinflated tires from growing into a much larger problem. The system is designed to warn the driver of a potential problem with their tire stability before the tire becomes a critical handling issue. Not to mention, fuel economy improves when tires are at the recommended pressures. Proper inflation can also extend tire life and contribute to the vehicle’s stability and safety.
When it comes to TPMS service, Scott Holloway, CEO of Bartec U.S.A. says: “The percentage of cars and trucks being serviced today that have TPMS is rapidly growing. We are approaching a time where the average aged vehicle [approximately 12 years old] is 100 percent covered by TPMS. In 2008, the TPMS Mandate became 100 percent effective in North America, which means those cars are nearly 12 years old, and they all have TPMS.”
Sheila Stevens, marketing manager at ATEQ, adds, “Sales of replacement sensors, such as universal aftermarket sensors, are steadily on the rise to increase as the batteries in OE sensors are reaching the end of their lifetime, and it's a great trend to stick to as a technician and shop owner.”
There’s no doubt with continuing improvements to the tire monitoring system, we will see a much safer driving mode in the future with improved handling, and more adaptive uses of tire inflation qualities as part of the overall monitoring of the vehicle. There’s no doubt it will improve handling, reduce tire wear, save on fuel and, most importantly, save lives.
Two types of TPMS
A major issue for any shop owner considering adding tire work to their shop is whether or not TPMS is a viable economic investment. So, let’s look at what a shop owner will need to think about in order to get into TPMS repair and replacement business at their shop.
First off, there are two types of systems you’ll need to be aware of: indirect and direct TPMS. Direct TPMS uses a sensor mounted as part of the valve stem, or as Ford used up to 2011 or so (as well as other manufacturers), a banded type of sensor that was clamped around the center of the wheel. Indirect TPMS uses the ABS wheel speed sensors to determine tire pressure by way of the overall rotational value (circumference of the tire), and calculates the tire pressure value that way.
Both are good at what they do, but there are some significant differences, and both will require different types of testing equipment.
The company Autel provides two types of TPMS tools, depending on the type of service the shop is providing. “Both our TS508 and TS608 provide complete TPMS coverage -- there is no TPMS tire service feature that they do not perform, including OE sensor cloning to quickly program a replacement sensor,” says Daniel Bemiss, Autel’s marketing director.
Pros and cons
Pros – Direct tire pressure monitoring systems deliver accurate pressure readings, and are operated by a G-force accelerometer as part of the valve stem or band. The entire unit is run by an internal battery (unserviceable). The battery life varies depending on who you ask. On most vehicles there is no need to reset after a basic tire rotation or inflation adjustments. Recalibration is only needed if a sensor or monitoring computer is replaced.
Cons – They can be more expensive to maintain (if/when sensors need to be replaced), and sensors can be damaged during tire installation if the technicians aren’t careful. On models with the automatic recalibration feature, be aware of the dreaded ‘parking lot’ recalibration. If you try to calibrate them with the vehicle sitting too close to another vehicle equipped with the same type of TPMS, it can actually pick up the frequency of the other car’s sensors, making your reset totally useless.
Pros – Indirect systems don’t need expensive sensors mounted in the tires. They use the ABS wheel speed sensors. Since there is no need for an internal battery that has a limited life span or a sensor in the wheel that can fail, theoretically, the system should last the life of the vehicle.
Cons – The readings may be inaccurate if you change tire size or the tires are worn unevenly. Also, if all four tires are underinflated due to neglect, the actual pressure values will be incorrect, and you may not be alerted to a stability problem despite all the tires being reported to the processor as being OK.
However, on some of the systems that problem has been corrected by requiring the actual tire size to be entered into the computer when programming; the computer has the calculations for the circumference and knows the tires are actually low (not with all vehicles, though).
If the rim size, or tire size is changed and the information isn’t entered into the PCM, the entire system is invalid. (Note: I’ve run across a tire size that was not listed in the PCM and therefore wasn’t able to reset that particular tire size to that particular car.
Most of these systems must be reset after tire rotations and/or inflation adjustments. Most of the time this is taken care of by simply driving the vehicle a few hundred yards, coming to a complete stop, and then moving forward again. Direct systems can sense the air pressure changes when there is an increase or decrease in pressure when you’re adding air to the tire, and in some cases, self-adjust. (Note: Some models with Direct TPMS will sound the horn when the proper air pressure is reached in each tire. A handy feature when you don’t have a pressure gauge handy.)
More tools and equipment
Depending on the area of the country and how long people drive their vehicles, technicians may be changing tire pressure monitoring systems due to the length of time they’re on the road. (If there is a vehicle with one low battery indicated by a service code, chances are the other ones aren’t far behind. Low battery indication is one of those features you’ll find on your TPMS tool).
A cloning tool would be a well-spent investment. These tools allow technicians to take the two different types of sensors (315MHZ and 433MHZ) and teach them the ID number from the original sensor. The sensors are typically less expensive (Warning: Some of the cheaper ones can be unpredictably faulty right out of the box) and allow users to take the original sensor, download the ID and reenter it into the cloned sensor. This way technicians don’t have to reflash the onboard computer with a new ID number.
“Bartec and the Schrader Company were the first to develop wireless sensor programming ‘at the vehicle’ with the introduction of the EZ-Sensor,” says Bartec’s Scott Holloway. “Our tool, based on make-model-year, would effectively program the “blank sensor” with the appropriate communication protocol and sensor ID.”
Some vehicles can ID the sensors on their own and don’t need a scanner, but like most everything else in the automotive world, nobody does it the same on every year, make or model in their lineup.
With Indirect TPMS, technicians need a scanner that can work with the ABS system of that manufacturer. These days, there are a number of off the shelf scanners that can do the job just as well, if not better, than the factory tool.
So, where’s the money at?
Maintaining an existing customer’s vehicles is obviously a shop owner's first concern, but there’s more to it. Aftermarket TPMS installations are becoming increasingly popular for RVs, large trucks, older passenger cars and even motorcycles. The amount of possible TPMS work out there is steadily growing. For those areas of the country with long winters, it’s very common for a customer to have a set of winter tires stashed in their garage that have TPMS installed. By next winter they’ll need those mounted and checked, and possibly have that particular ID entered into the PCM. Note: for every 10 degrees the temperature drops, the tire pressure will drop by 1 psi.
ATEQ’s Sheila Stevens raises a good point: “Technicians who are not educating themselves on TPMS are missing out on TPMS service sales including sensor sales and services, alignment and rotation services, TPMS reset (relearn) services and more,” she says. “In addition, sending customers back to the dealer with a simple TPMS issue can put a damper on independent shops’ reputation.”
As with everything else in the automotive world, nothing remains the same. Manufacturers have already incorporated stability controls reducing side slip and traction issues into the tire monitoring systems as part of their overall evaluation of road conditions and handling issues. But, there’s also talk about incorporating reduced engine performance modes and shift point changes due to tire inflation. It could go as far as determining whether or not the adaptive cruise control should be turned off or remain on if the tire pressure isn’t maintained.
If you think about it, only a small patch of tire is the only thing between your vehicle and the road surface, and any additional information that can be gathered can only enhance the computer’s ability to react to the changing road conditions with greater accuracy and speed.
As a rule, as vehicle technology evolves, the more interdependent the technology becomes. “Smart vehicles” increasingly rely on data and input from sensors located throughout the vehicle system.
The data from TPMS is hugely critical in keeping other systems performing as designed. We know that vehicle control and performance are greatly impacted by tire pressure. Things like stopping distance and cornering change drastically when tire pressures are low. As TPMS sensors evolve, there will likely be more data points available as well. It all adds up to more diagnostic business in your shop, and safer vehicles on the road.