What Does Service Tire Monitor System Mean? Tire Pressure Monitoring System (TPMS)
A Tire Pressure Monitoring System (TPMS) is an electronic system designed to monitor the air pressure inside pneumatic tires on various types of vehicles.
TPMS detects when one or more of a vehicle’s tires are under-inflated and alerts the driver.
TPMS works by means of pressure sensors attached to each tire’s valve stem.
The sensors continuously monitor and measure the air pressure in each tire and transmit this data to a central computer module.
The module analyzes the pressure information and can detect when the air pressure drops below a programmed threshold.
When under-inflation is detected, the TPMS triggers a warning indicator light on the vehicle’s instrument cluster to alert the driver.
This warning light is sometimes referred to as the TPMS warning light or low tire pressure warning light.
Most TPMS systems will display which specific tire is under-inflated once the vehicle is stopped.
TPMS became a mandatory feature in all new passenger vehicles sold in the United States starting in 2007, as mandated by the TREAD Act.
The technology helps improve road safety and fuel economy by preventing tires from becoming dangerously under-inflated.
Keeping tires properly inflated also reduces tire wear and damage.
Types of Tire Pressure Monitoring Systems
There are two main types of Tire Pressure Monitoring Systems (TPMS) – direct and indirect.
Direct TPMS
Direct TPMS use sensors attached to each wheel that directly measure the air pressure in each tire.
The tire pressure sensors have batteries that need to be replaced periodically, usually around every 5-7 years.
The sensors broadcast tire pressure data via radio frequency signals to a receiver module in the vehicle.
Direct TPMS provides the most accurate tire pressure readings since it is directly measuring the pressure in each tire.
It can tell you exactly which tire is underinflated if one has low pressure.
Direct TPMS is mandated in the United States on all light passenger vehicles from 2008 onwards.
Indirect TPMS
Indirect TPMS does not use physical sensors attached to each wheel.
Instead, it monitors the wheel speed sensors of the anti-lock brake system (ABS) to detect underinflation.
If a tire has lower pressure, its diameter decreases slightly. This causes the wheel to rotate faster compared to the other tires.
By monitoring relative differences in wheel speeds, the indirect TPMS system can infer if a tire has low pressure.
The main advantage of indirect TPMS is that no additional sensors or transmitters have to be fitted on the wheels, reducing costs.
However, it cannot provide the exact tire pressure or tell you which specific tire has low pressure.
Indirect TPMS may not detect underinflation as accurately or as quickly as direct systems.
It is more prone to false alerts when tire pressures are affected by temperature changes or different tires/wheels.
Differences between direct and indirect TPMS
The key differences between direct and indirect TPMS:
- Direct TPMS uses physical tire pressure sensors on each wheel, while indirect TPMS uses existing ABS wheel speed sensors.
- Direct TPMS provides exact tire pressure readings for each tire and can pinpoint the underinflated tire. Indirect TPMS cannot provide the tire pressure or identify the low tire.
- Direct TPMS sensors have batteries that need occasional replacement. Indirect TPMS has no extra sensors or batteries.
- Direct TPMS offers more accurate and faster detection of tire underinflation compared to indirect systems.
- Direct TPMS meets regulatory requirements for TPMS in the United States. Indirect TPMS may not detect underinflation as reliably.
So in summary, direct TPMS provides more advanced pressure monitoring capabilities, while indirect TPMS is a more basic and low-cost system.
Direct TPMS is generally considered superior and is mandated in the US, but indirect systems can also warn drivers about potential tire underinflation.
Purpose and Benefits of TPMS
A tire pressure monitoring system provides several important benefits:
Improves Fuel Economy
Keeping tires inflated to the proper pressure can significantly improve fuel economy.
Underinflated tires create more rolling resistance, forcing the engine to work harder and use more fuel.
Studies show that having just one tire underinflated by 25% can reduce fuel economy by up to 3%.
Maintaining proper inflation through TPMS helps optimize gas mileage.
Extends Tire Life
Underinflated tires wear out more quickly and unevenly.
The added stress from lower pressure causes faster tread wear.
TPMS alerts drivers so tires can be re-inflated to the proper level, extending their lifespan.
This saves money by reducing tire replacement costs. Proper inflation also helps prevent tire failures.
Enhances Vehicle Safety
Incorrect tire pressure impacts handling, braking distance, and control.
Significantly underinflated tires can lead to blowouts, especially at highway speeds.
TPMS provides an early warning system, so any issues can be addressed before they become dangerous.
Keeping tires at the vehicle manufacturer’s recommended pressure through TPMS improves stability, steering responsiveness, and braking performance.
TPMS Warning Light
The TPMS warning light is located on your vehicle’s instrument cluster, often on the dashboard.
It looks like a horseshoe with an exclamation point in the middle.
When the TPMS warning light illuminates, it means that one or more of your tires is significantly underinflated.
A tire that is underinflated by 25% or more will trigger the TPMS warning light.
This indicates a potentially serious condition that needs immediate attention, as driving on a severely underinflated tire can lead to a blowout or other unsafe scenarios.
The TPMS system compares the air pressure in each tire to the recommended inflation level set by the vehicle manufacturer.
If the pressure drops too far below the threshold, the system will detect the underinflation and turn on the TPMS warning light to alert the driver.
Don’t ignore the TPMS warning light or try to drive further with it on.
Safely pull over, check all the tires‘ pressure levels, and inflate any underinflated tires to the recommended PSI.
This will turn off the TPMS warning light once the system detects the tires are properly inflated again.
TPMS Malfunction and Service Indicators
There are two different types of warning lights related to tire pressure – the TPMS warning light and the TPMS service indicator.
It’s important to understand the difference between the two.
The TPMS warning light looks like an exclamation point inside a horseshoe and illuminates when one or more of your tires is significantly under-inflated.
This light indicates that tire pressure should be checked and adjusted as needed.
Driving on severely underinflated tires can lead to poor handling, reduced fuel economy, and increased risk of damage or blowouts.
The TPMS service indicator is sometimes called the TPMS malfunction light. This looks like a wrench or tool icon.
If it illuminates, it means there is a problem with the TPMS system itself, not the tire pressure.
This could be caused by failed sensors, a faulty control module, or some other issue with the monitoring system.
The service light does not mean your tire pressure is low.
However, the TPMS will not be able to alert you of any underinflation until the malfunction is fixed.
So in summary:
- TPMS warning light indicates low tire pressure
- TPMS service light indicates a system malfunction
Both lights should prompt you to take action – low pressure requires inflating tires, and a TPMS malfunction requires service to restore system functionality.
Knowing the difference between the two can help you understand whether air needs to be added or if the TPMS itself needs repair.
Causes of TPMS Errors
One of the most common reasons for TPMS errors is low tire pressure.
Over time, tires naturally lose air pressure due to slow leaks or diffusion through the rubber.
TPMS sensors can detect when the air pressure falls below the vehicle manufacturer’s recommended level and trigger a warning light.
Maintaining proper inflation as specified in the owner’s manual can help avoid errors due to low tire pressure.
Faulty tire pressure sensors are another source of TPMS error messages.
The sensors contain batteries that eventually wear out over 5-10 years of use.
Extreme temperature fluctuations and moisture can also damage sensors.
Damaged sensors may transmit inaccurate readings or stop communicating with the vehicle computer.
Replacing faulty sensors can resolve TPMS errors.
Interference from external devices that operate on the same radio frequency as TPMS can disrupt sensor signals.
Aftermarket or non-OEM wheels and tires using incompatible TPMS sensors are a common source of interference.
Devices like radio transmitters and LED lights that emit high levels of electromagnetic radiation near the sensors can also interfere with them.
Checking for incompatible components and electromagnetic sources near the wheels may be necessary to resolve interference issues.
How to Reset TPMS
Resetting the TPMS after tire rotation or replacement helps the system relearn the new tire locations and pressures.
There are two main ways to reset TPMS:
Via Vehicle Settings Menu
Many modern vehicles have a TPMS reset option in the settings menu on the dashboard information display.
Follow these general steps:
- Turn the ignition on and inflate your tires to the recommended pressure on the tire placard.
- Locate the TPMS reset option, which may be under a “Vehicle Information”, “Tire Pressure”, or similar menu.
- Select the reset or calibration option.
- Drive for around 15 minutes above 15 mph to allow the system to reset and recognize each tire’s location and pressure.
Using a TPMS Reset Tool
A TPMS reset tool can reset the system without needing to access the vehicle settings. Follow these steps:
- Inflate your tires to the recommended pressure first.
- Activate the reset tool and hold it near the tire’s valve stem to trigger a reset for that tire. The tool’s light may flash when successful.
- Repeat this for each tire to reset the entire TPMS.
- Drive for around 15 minutes above 15 mph to complete the reset.
The reset tool is simple and quick to use but requires purchasing an additional tool if you don’t already have one.
Check your vehicle manual for any model-specific reset instructions.
TPMS Maintenance
Properly maintaining your TPMS will ensure it continues functioning accurately.
This involves regular tire rotations, replacing tires and sensors as needed, and replacing sensor batteries.
- Rotating your tires every 5,000-8,000 miles helps prevent uneven wear and ensures the TPMS sensors get evenly used.
- When rotating tires, you must retrain the TPMS sensors to their new location on the vehicle. This requires a TPMS relearn tool or resetting the sensors so they match their new tire position.
- Over time, tires wear out and need replacement. When installing new tires, new TPMS sensors are usually required.
- The new TPMS sensors must be activated and programmed to sync with your vehicle. A professional installer will take care of this during the tire change.
Sensor Batteries
- TPMS sensors are powered by long-life batteries that last 5-10 years on average.
- When the sensor battery runs low, the TPMS light will illuminate indicating a problem. The sensor battery must be replaced.
- Replacing the battery requires dismounting the tire and replacing the entire sensor. A tire shop can perform this service.
Proper TPMS maintenance ensures you get the most out of your tire pressure monitoring system for safety and performance.
Pay attention to the TPMS warning lights and service the system accordingly.
TPMS Costs
The cost of maintaining your TPMS can vary, but typically averages around $150-$200.
The most common costs associated with TPMS maintenance include:
- Sensor Replacement Costs – Each tire pressure sensor can cost $50-$100 to replace, depending on the vehicle make and model. Most vehicles have 4 sensors (one per tire), so a full replacement may cost around $200-$400 for parts. Labor costs will also apply for installation.
- Diagnostic Fees – Many mechanics charge diagnostic fees ($75-$150 typically) to determine if any TPMS sensors need to be replaced. They will scan the system to see which (if any) sensors are malfunctioning before recommending replacement. This avoids unnecessary sensor replacements.
Other costs to keep in mind are tire rotation/balancing, which may be required after new TPMS sensor installation.
And any costs associated with fixing the underlying problem, such as a nail in the tire causing air leaks and triggering the TPMS light.
The costs may seem high, but a functioning TPMS provides important safety and performance benefits.
Proper tire inflation is critical for control and braking. So keeping your TPMS in working order is worth the investment, especially compared to the risks of driving with underinflated tires.
The Future of TPMS
Tire pressure monitoring systems are likely to become even more common in the future as regulations require them in more vehicles.
In the United States, all new passenger vehicles have been required to have TPMS since 2007 per the TREAD Act.
However, regulations in other parts of the world are still catching up. For example, TPMS will be mandatory for all new cars sold in the European Union starting in 2022.
Several other countries are expected to pass similar regulations in the coming years.
As TPMS becomes standard worldwide, automakers and suppliers will continue innovating new TPMS technologies. Some areas of development include:
- Improved sensor battery life – New batteries can last up to 10 years without needing replacement.
- Tire pressure sensors that monitor temperature – This helps detect when a tire is over- or under-inflated for the temperature.
- Next generation sensors – Smaller, more durable sensors that are easier to install and replace.
- TPMS with central tire inflation systems – These can automatically inflate each tire to the optimal pressure.
- Connected TPMS – Sensors that connect to a vehicle’s infotainment system and provide real-time pressure updates to the driver.
- Autonomous TPMS – Uses advanced algorithms to predict tire issues before they happen.
As TPMS becomes standard worldwide, they will provide even more safety and performance benefits to everyday drivers.
And new innovations will continue modernizing and improving tire pressure monitoring.
