Lexus GX 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 GX, and how you can reset it.
The TPMS warning light illuminates in Lexus GX 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 GX, 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 GX 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. These are official cold tire pressure values for GX 350 from Lexus as per the 2020 owners manual.
- 235/45R18 94Y: 35 psi
- P235/45R18 94V: 35 psi
- 235/40R19 96Y XL (front): 35 psi
265/35R19 94Y (rear): 36 psi
- 235/40R19 96Y XL: Front: 35 psi, Rear: 36 psi
- 235/40R19 96V XL: Front: 35 psi, Rear: 36 psi
- T155/70D17 110M: 60 psi
- T145/70D18 107M: 60 psi
Resetting the TPMS warning light
After you have inflated all the tires to the correct air pressure, the TPMS warning light should turn off automatically after driving for a few miles. Lexus GX uses the direct method for monitoring tire pressure, which means a pressure sensor actively records the internal pressure of the tire on each wheel. If the warning light doesn’t turn off you should perform a reset procedure.
The tire pressure warning system must be initialized in the following circumstances:
- When rotating the tires.
- When the tire inflation pressure is changed such as when changing traveling speed or load weight.
- When changing the tire size.
When the tire pressure warning system is initialized, the current tire inflation pressure is set as the benchmark pressure.
TPMS Reset Procedure for Lexus GX
- Park the vehicle in a safe place and turn the engine switch off.
- Adjust the tire inflation pressure to the specified cold tire inflation pressure level.
- Turn the engine switch to IGNITION ON mode.
- Select the Settings tab in the instrument cluster settings.
- Select Vehicle Settings.
- Select TPMS.
- Then press and hold O button on the steering wheel until the tire pressure warning light starts blinking.
- A message is displayed on the multi-information display. Also, “–” is displayed for inflation pressure of each tire on the multiinformation display while the tire pressure warning system determines the position.
- Drive the vehicle at approximately 25mph (40 km/h) or more for approximately 10 to 30 minutes.
When initialization is complete, the inflation pressure of each tire will be displayed on the multi-information display. Depending on the vehicle and driving conditions, initialization may take up to approximately 1 hour to complete.
WARNING! Do not reset the TPMS system without first adjusting the tire inflation pressure to the specified level. Otherwise, the tire pressure warning light may not come on even if the tire inflation pressure is low, or it may come on when the tire inflation pressure is actually normal.
TPMS reset guidelines
- Make sure to carry out initialization after adjusting the tire inflation pressure. Also, make sure the tires are cold before carrying out initialization or tire inflation pressure adjustment.
- The tire pressure warning system can be initialized by yourself, but depending on the driving conditions and driving environment, initialization may take some time to complete.
- If you have accidentally turned the engine switch off during initialization, it is not necessary to manually restart the initialization again, as initialization will restart automatically the next time the engine switch is turned to IGNITION ON mode.
- If you accidentally perform initialization when initialization is not necessary, adjust the tire inflation pressure to the specified level when the tires are cold, and conduct initialization again.
- While the position of each tire is being determined and the inflation pressures are not being displayed on the multiinformation display, if the inflation pressure of a tire drops, the tire pressure warning light will come on.
If the tire pressure warning system is not initialized properly
In the following situations, initialization may take longer than usual to be completed or may not be possible. (Usually, the vehicle will need to be driven for approximately 10 to 30 minutes to complete initialization.) If initialization is not complete after driving approximately 30 minutes, continue driving for a while.
- If the vehicle is driven on an unpaved road, it may take longer to complete initialization.
- If the vehicle is backed up while performing initialization, data collected during initialization will be cleared and it will take longer than normal to complete.
- If the vehicle is driven in heavy traffic or another situation where other vehicles are driven close by, it may take time for the system to recognize the tire pressure warning valve and transmitters of your vehicle over those of other vehicles.
If initialization is not complete after driving for approximately 1 hour, park the vehicle in a safe place for approximately 20 minutes and then drive the vehicle again.
In the following situations, initialization will not be started or was not completed properly and the system will not operate properly. Perform the initialization procedure again.
- If, when attempting to start initialization, the tire pressure warning light does not blink 3 times.
- If, when the vehicle has been driven for about 20 minutes after performing initialization, the tire pressure warning light blinks for approximately 1 minute and then illuminates.
If initialization cannot be completed after performing the above procedure, contact your Lexus dealer.
Chilly weather can turn on low tire pressure light in GX
Cold weather is one of the most common cause for low tire pressure warning light in Lexus GX. 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 GX. 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 GX 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 GX 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 GX 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 GX with low tire pressure?
The driving characteristics of GX 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 GX 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 GX. 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 GX. 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 GX, 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.
Lexus GX TPMS user guide
Your vehicle is equipped with a tire pressure warning system that uses tire pressure warning valves and transmitters to detect low tire inflation pressure before serious problems arise.
The tire pressure detected by the tire pressure warning system can be displayed on the multi-information display.
If the tire pressure drops below a predetermined level, the driver is warned by a screen display and a warning light.
Routine tire inflation pressure checks
The tire pressure warning system does not replace routine tire inflation pressure checks. Make sure to check tire inflation pressure as part of your routine of daily vehicle checks.
Tire inflation pressure
It may take a few minutes to display the tire inflation pressure after the engine switch is turned to IGNITION ON mode. It may also take a few minutes to display the tire inflation pressure after inflation pressure has been adjusted. Tire inflation pressure changes with temperature. The displayed values may also be different from the values measured using a tire pressure gauge.
Situations in which the tire pressure warning system may not operate properly
In the following cases, the tire pressure warning system may not operate properly.
- If non-genuine Lexus wheels are used.
- If a tire has been replaced with a tire that is not an OE (Original Equipment) tire.
- If a tire has been replaced with a tire that is not of the specified size.
- If tire chains, etc. are installed.
- An auxiliary-supported run-flat tire is equipped.
- If a window tint that affects the radio wave signals is installed.
- If there is a lot of snow or ice on the vehicle, particularly around the wheels or wheel housings.
- If the tire inflation pressure is extremely higher than the specified level.
- If tires not equipped with tire pressure warning valves and transmitters are used.
- If the ID code on the tire pressure warning valves and transmitters is not registered in the tire pressure warning computer.
Performance may be affected in the following situations.
- When driving near a TV tower, electric power plant, gas station, radio station, large display, airport or other facility that generates strong radio waves or electrical noise.
- When carrying a portable radio, cellular phone, cordless phone or other wireless communication device
If tire position information is not correctly displayed due to the radio wave conditions, the display may be corrected by driving and changing the radio wave conditions.
When the vehicle is parked, the time taken for the warning to start or go off could be extended.
When tire inflation pressure declines rapidly for example when a tire has burst, the warning may not function.
Warning performance of the tire pressure warning system
The warning of the tire pressure warning system will change in accordance with driving conditions. For this reason, the system may give a warning even if the tire pressure does not reach a low enough level, or if the pressure is higher than the pressure that was adjusted to when the system was initialized.
Installing tire pressure warning valves and transmitters
When replacing the tires or wheels, the tire pressure warning valve and transmitters must be installed to the wheels which will be installed to the vehicle. When new tire pressure warning valves and transmitters are installed, new ID codes must be registered in the tire pressure warning computer and the tire pressure warning system must be initialized.
Replacing tires and wheels
If the ID code of the tire pressure warning valve and transmitter is not registered, the tire pressure warning system will not work properly. After driving for about 20 minutes, the tire pressure warning light blinks for 1 minute and stays on to indicate a system malfunction.
Repairing or replacing tires, wheels, tire pressure warning valves, transmitters and tire valve caps
- When removing or fitting the wheels, tires or the tire pressure warning valves and transmitters, contact your Lexus dealer as the tire pressure warning valves and transmitters may be damaged if not handled correctly.
- Make sure to install the tire valve caps. If a tire valve cap is not installed, water may enter the valve and cause it to corrode, possibly leading to the valve sticking or air to leak from the tire.
- When replacing tire valve caps, do not use tire valve caps other than those specified. The cap may become stuck.
To avoid damage to the tire pressure warning valves and transmitters
When a tire is repaired with liquid sealants, the tire pressure warning valve and transmitter may not operate properly. If a liquid sealant is used, contact your Lexus dealer or other qualified service shop as soon as possible. After use of liquid sealant, make sure to replace the tire pressure warning valve and transmitter when repairing or replacing the tire.
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 GX. 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 GX, 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 GX?
No, the TPMS system is federally mandated, and cannot be disabled in Lexus GX. All vehicles must have a working tire pressure monitoring system to be legally compliant.
Use OBD2 scanner for diagnosis
Since Lexus GX 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.