Mazda MX-5 is equipped with Tire Pressure Monitoring System (TPMS) for the purpose of warning the driver when one or more of the tires are significantly under-inflated, creating a potentially unsafe driving condition. In this article we discuss the reasons for the amber colored TPMS warning light in MX-5, and how you can reset it.
The TPMS warning light illuminates in Mazda MX-5 when air pressure is low in one or more of the tires, battery has depleted in a pressure sensor, TPMS receiver module has malfunctioned, or a pressure sensor has been damaged.
Low tire pressure
When the amber colored TPMS warning light 
turns on in your MX-5, stop your vehicle when it is safe to do so and check tire pressure on all the wheels, including the spare wheel (if your vehicle has one). Driving on a significantly under-inflated tire causes the tire to overheat and can lead to tire failure.
Reinflate the tires
Reinflate all the tires of your MX-5 to the manufacturer specified air pressure, which is mentioned on the vehicle placard or tire inflation pressure label usually located on the B-pillar or the edge of the driver door. If you can’t find the label, check the size of your tire which is mentioned on the sidewall of the tire, and match it to the tire pressure information shown below.
- 195/50R16 84V: 29 psi
- 205/45R17 84W: 29 psi
Resetting the TPMS warning light
After you have inflated all the tires to the correct air pressure, the TPMS warning light will turn off automatically. Mazda MX-5 uses the direct method for monitoring tire pressure, which means a pressure sensor actively records the internal pressure and air temperature of the tire on each wheel. There is no need to reinitialize the TPMS system in order to reset the warning light. There is no reset button like the one you see in vehicles with indirect TPMS system which uses ABS sensors to detect low tire pressure.
If the low tire pressure light does not turn off automatically after reinflating the tires in your MX-5, increase the tire pressure by 5 psi on top of the factory recommended value, and drive your vehicle for at least 10 miles (16 km). After the TPMS warning light turns off, and the vehicle has been parked for a few hours, reduce the tire pressure to the factory recommended value.
Chilly weather can turn on low tire pressure light in MX-5
Cold weather is one of the most common cause for low tire pressure warning light in Mazda MX-5. When analyzing WheelsJoint’s statistical data, it has been observed that there is sharp rise in the number of searches for TPMS warning light causes at the start of every winter season, about three times higher as compared to mid summer season.
The air, like most other substances, expands when heated and contracts when cooled. So when the weather gets colder, the tire pressure decreases, which could trigger TPMS warning light in MX-5. The tire pressure will vary with temperature by about 1 psi (7 kPa) for every 12°F (6.5°C).
Inflate tires when cold
Tire pressure in MX-5 should always be set based on cold inflation tire pressure. This is defined as the tire pressure after the vehicle has not been driven for at least three hours, or driven less than 1 mile (1.6 km) after a three-hour period.
Do not adjust tire pressure when hot
The tires on your MX-5 can get around 50 degrees hotter than the outside temperature when you’re driving, which increases the tire pressure by about 4 psi – this is normal and there should be no adjustment for this increased pressure.
Does altitude affect tire pressure?
Yes, altitude can change tire pressure values, but it is negligible and not a cause for concern. If you drive your MX-5 from sea level to Mount Evans Scenic Byway in Colorado which is the highest paved road in North America at the altitude of 14,130 feet (4,307 m), the tire pressure should theoretically increase by approximately 6 psi. But, the decrease in ambient temperature at higher elevation contracts the air in tires and compensates for any altitude pressure changes.
Is it safe to drive MX-5 with low tire pressure?
The driving characteristics of MX-5 change even if the air pressure is 5 psi less than manufacturer’s recommended value: the braking distance can be longer, cornering worse, and at particularly high speeds there is even a risk that the tire will burst. Low tire pressure also increases tire wear, and the higher rolling resistance of the tire means higher fuel consumption. So it is recommended to reinflate the tires to the correct pressure as soon as possible.
Dead battery in a tire pressure sensor
Each tire pressure sensor in MX-5 is powered by a built-in lithium-ion battery. When the battery is depleted, the sensor stops transmitting tire pressure information to the receiver module. When this happens, the TPMS warning light will flash every time the engine is started, and will remain illuminated until you turn off the vehicle.
How long do the pressure sensor batteries last?
The tire pressure sensor batteries usually last anywhere from 5 to 10 years in MX-5. When the battery is depleted, you must replace the sensor itself, as the battery is sealed into the sensor unit and is non-replaceable.
Identifying a faulty pressure sensor
The most reliable method for detecting a faulty tire pressure sensor or a sensor with dead battery is by testing each sensor with a scan tool. For example, MaxiTPMS TS408 is commonly used for diagnosing and programming tire pressure sensors. A sensor that is not detectable by the scanner is most likely defective and should be replaced with a new one.
If you don’t want to spend over a hundred bucks on a scanner, then head over to any reputable tire shop and perform a TPMS diagnostic scan of your MX-5. Some shops like Discount Tire and Pep Boys offer free of charge TPMS diagnostic services.
Installed new tires?
If a pressure sensor stopped responding after you installed new tires on your MX-5, it is possible the sensor got damaged during tire installation. These sensors are quite sensitive, and can be easily damaged if utmost care is not taken while changing tires.
Mazda MX-5 TPMS user guide
System Error Activation
When the warning light flashes, there may be a system malfunction. Consult an Authorized Mazda Dealer.
A system error activation may occur in the following cases:
- When there is equipment or a device near the vehicle using the same radio frequency as that of the tire pressure sensors.
- When a metallic device such as a non-genuine navigation system is equipped near the center of the dashboard, which may block radio signals from the tire pressure sensor to the receiver unit.
- When using the following devices in the vehicle that may cause radio interference with the receiver unit.
- A digital device such as a personal computer.
- A current converter device such as a DC-AC converter.
- When excess snow or ice adheres to the vehicle, especially around the wheels.
- When the tire pressure sensor batteries are exhausted.
- When using a wheel with no tire pressure sensor installed.
- When using tires with steel wire reinforcement in the sidewalls.
- When using tire chains.
Changing tires and wheels
The following procedure allows the TPMS to recognize a tire pressure sensor’s unique ID signal code whenever tires or wheels are changed, such as changing to and from winter tires.
Note: Each tire pressure sensor has a unique ID signal code. The signal code must be registered with the TPMS before it can work. The easiest way to do it is to have an Authorized Mazda Dealer, change your tire and complete ID signal code registration.
When having tires changed at an Authorized Mazda Dealer
When an Authorized Mazda Dealer, changes your vehicle’s tires, they will complete the tire pressure sensor ID signal code registration.
When changing tires yourself
If you or someone else changes tires, you or someone else can also undertake the steps for the TPMS to complete the ID signal code registration.
- After tires have been changed, switch the ignition ON, then back to ACC or OFF.
- Wait for about 15 minutes.
- After about 15 minutes, drive the vehicle at a speed of at least 25 km/h (16 mph) for 10 minutes and the tire pressure sensor ID signal code will be registered automatically
If the vehicle is driven within about 15 minutes of changing tires, the tire pressure monitoring system warning light will flash because the sensor ID signal code would not have been registered. If this happens, park the vehicle for about 15 minutes, after which the sensor ID signal code will register upon driving the vehicle for 10 minutes.
Reset the entire system
If the low tire pressure warning light won’t turn off due to a glitch in the tire pressure monitoring system, it may be possible to reset the TPMS system by resetting all on-board computers in your MX-5. This method should only be considered as a last resort, when all else fails.
You can reboot all the on-board computers by disconnecting the main 12 volt battery for a few minutes. Remove the cable from the negative terminal of the battery first, then from the positive terminal. With the battery disconnected, press the horn button a few times and turn on the headlights to drain out all the residual electricity from the system. After about 15 minutes, reconnect the battery in reverse order: positive cable first, then negative cable.
Tire pressure keeps getting low
If the TPMS warning light turns on frequently in your MX-5, and the tire pressure is also decreasing after you have reinflated the tires, there may be an air leak. One or more of the tires may have been punctured by an external object, or the air may be leaking from a defective value stem.
Can I disable the TPMS system in MX-5?
No, the TPMS system is federally mandated, and cannot be disabled in Mazda MX-5. All vehicles must have a working tire pressure monitoring system to be legally compliant.
Use OBD2 scanner for diagnosis
Since Mazda MX-5 is equipped with on-board diagnostics (OBD), a fault diagnosis can provide initial indications of where the malfunction is located. But when it comes to TPMS, a basic code reader will not suffice. You will need an advanced scanner to monitor TPMS data or read TPMS codes.
BlueDriver is a commonly used scanner by DIYers that can read TPMS codes for most vehicles and isn’t too expensive – costs about a hundred bucks. You can also clear the TPMS fault codes with this device which will turn off the warning light, but the light may come back on if the on-board diagnostic system detects a fault again.
