Ford C-Max 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 C-Max, and how you can reset it.
The TPMS warning light illuminates in Ford C-Max 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 C-Max, 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 C-Max 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 C-Max from Ford.
- P225/50R17 93V: 38 psi (Hybrid US version)
Resetting the TPMS warning light in Ford C-Max Hybrid (US Version)
After you have inflated all the tires to the correct air pressure, the TPMS warning light will turn off automatically. Ford C-Max 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. Just drive your vehicle and the light will turn off after a few miles.
If the low tire pressure light does not turn off automatically after reinflating the tires in your C-Max, 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.
TPMS reset after tire rotation: You will need to relearn all the TPMS sensors on your Ford C-Max after rotating tires.
Video: TPMS reset procedure
TPMS reset (EU version)
In the EU version of Ford C-Max, you can reset the TPMS system from the instrument cluster settings.
Ford advises to reset the TPMS system following any adjustment to the tire pressures or after any changing of tires.
- Using the information display control, navigate to Settings > Driver assist > Deflation detection.
- Press and hold the OK button until confirmation appears.
Note: Do not reset the system when the vehicle is moving.
Chilly weather can turn on low tire pressure light in C-Max
Cold weather is one of the most common cause for low tire pressure warning light in Ford C-Max. 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 C-Max. 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 C-Max 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 C-Max 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 C-Max 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 C-Max with low tire pressure?
The driving characteristics of C-Max 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 C-Max 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 C-Max. 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 C-Max. 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 C-Max, 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.
Ford C-Max TPMS user guide
Each tire, including the spare (if provided), should be checked monthly when cold and inflated to the inflation pressure recommended by the vehicle manufacturer on the vehicle placard or tire inflation pressure label. (If your vehicle has tires of a different size than the size indicated on the vehicle placard or tire inflation pressure label, you should determine the proper tire inflation pressure for those tires).
Note: You should only use tire sealants in roadside emergencies as they may cause damage to the tire pressure monitoring system sensor.
As an added safety feature, your vehicle has been equipped with a Tire Pressure Monitoring System (TPMS) that illuminates a low tire pressure telltale when one or more of your tires is significantly under-inflated. Accordingly, when the low tire pressure telltale illuminates, you should stop and check your tires as soon as possible, and inflate them to the proper pressure. Driving on a significantly under-inflated tire causes the tire to overheat and can lead to tire failure. Under-inflation also reduces fuel efficiency and tire tread life, and may affect the vehicle’s handling and stopping ability.
Please note that the TPMS is not a substitute for proper tire maintenance, and it is the driver’s responsibility to maintain correct tire pressure, even if under-inflation has not reached the level to trigger illumination of the TPMS low tire pressure telltale.
Your vehicle has also been equipped with a TPMS malfunction indicator to indicate when the system is not operating properly. The TPMS malfunction indicator is combined with the low tire pressure telltale. When the system detects a malfunction, the telltale will flash for approximately one minute and then remain continuously illuminated. This sequence will continue upon subsequent vehicle start-ups as long as the malfunction exists.
When the malfunction indicator is illuminated, the system may not be able to detect or signal low tire pressure as intended. TPMS malfunctions may occur for a variety of reasons, including the installation of replacement or alternate tires or wheels on the vehicle that prevent the TPMS from functioning properly. Always check the TPMS malfunction telltale after replacing one or more tires or wheels on your vehicle to ensure that the replacement or alternate tires and wheels allow the TPMS to continue to function properly.
Changing Tires With a Tire Pressure Monitoring System
Each road tire is equipped with a tire pressure sensor located inside the wheel and tire assembly cavity. The pressure sensor is attached to the valve stem. The pressure sensor is covered by the tire and is not visible unless the tire is removed. Take care when changing the tire to avoid damaging the sensor
Understanding Your Tire Pressure Monitoring System
The tire pressure monitoring system measures pressure in your four road tires and sends the tire pressure readings to your vehicle. The low tire pressure warning light will turn on if the tire pressure is significantly low. Once the light is illuminated, your tires are under-inflated and need to be inflated to the manufacturer’s recommended tire pressure. Even if the light turns on and a short time later turns off, your tire pressure still needs to be checked.
When Your Temporary Spare Tire is Installed
When one of your road tires needs to be replaced with the temporary spare, the system will continue to identify an issue to remind you that the damaged road wheel and tire assembly needs to be repaired and put back on your vehicle. To restore the full function of the tire pressure monitoring system, have the damaged road wheel and tire assembly repaired and remounted on your vehicle.
When You Believe Your System is Not Operating Properly
The main function of the tire pressure monitoring system is to warn you when your tires need air. It can also warn you in the event the system is no longer capable of functioning as intended. See the following chart for information concerning your tire pressure monitoring system:
Solid warning light: Tire(s) under-inflated. Make sure tires are at the proper pressure. See Inflating your tires in this chapter. After inflating your tires to the manufacturer’s recommended pressure as shown on the Tire Label (located on the edge of driver’s door or the B-Pillar), the vehicle must be driven for at least two minutes over 20 mph (32 km/h) before the light turns off.
Solid warning light: Spare tire in use. Repair the damaged road wheel and tire assembly and reinstall it on the vehicle to restore system function.
Solid warning light: TPMS malfunction. If the tires are properly inflated and the spare tire is not in use but the light remains on, contact your authorized dealer as soon as possible.
Flashing warning light: Spare tire in use. Repair the damaged road wheel and tire assembly and reinstall it on the vehicle to restore system function.
Flashing warning light: TPMS malfunction. If the tires are properly inflated and the spare tire is not in use but the light remains on, contact your authorized dealer as soon as possible.
When Inflating Your Tires
When putting air into your tires (such as at a gas station or in your garage), the tire pressure monitoring system may not respond immediately to the air added to your tires. It may take up to two minutes of driving over 20 mph (32 km/h) for the light to turn off after you have filled your tires to the recommended inflation pressure.
How Temperature Affects Your Tire Pressure
The tire pressure monitoring system monitors tire pressure in each pneumatic tire. While driving in a normal manner, a typical passenger tire inflation pressure may increase about 2–4 psi (14–28 kPa) from a cold start situation. If the vehicle is stationary overnight with the outside temperature significantly lower than the daytime temperature, the tire pressure may decrease about 3 psi (21 kPa) for a drop of 30°F (17°C) in ambient temperature. This lower pressure value may be detected by the tire pressure monitoring system as being significantly lower than the recommended inflation pressure and activate the system warning light for low tire pressure. If the low tire pressure warning light is on, visually check each tire to verify that no tire is flat. If one or more tires are flat, repair as necessary. Check the air pressure in the road tires. If any tire is under-inflated, carefully drive the vehicle to the nearest location where air can be added to the tires. Inflate all the tires to the recommended inflation pressure.
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 C-Max. 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 C-Max, 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 C-Max?
No, the TPMS system is federally mandated, and cannot be disabled in Ford C-Max. All vehicles must have a working tire pressure monitoring system to be legally compliant.
Use OBD2 scanner for diagnosis
Since Ford C-Max 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.