Radio Frequency Interference

Radio Frequency Interference (RFI) can be caused by:

• Video equipment has been found to cause Radio Frequency Interference (RFI) especially when the video and power supply lines are near the TPMS.
• Car alarms (even those installed by the dealership) have been found to create enough Radio Frequency Interference (RFI) to cause the TPMS to malfunction or lose considerable range. These car alarms can be difficult to locate, as they are usually hidden somewhere out of the way for reduced accessibility.
• Many in-vehicle cell phone chargers have been found to cause considerable Radio Frequency Interference (RFI). The vehicles with the power point closest to the BCM are the most affected. It must be noted that most cell phone chargers do not produce high levels of Radio Frequency Interference (RFI) all the time. This depends on the state of charge of the cell phone battery. The phone battery must be almost completely discharged in some cases.
• Power supplies and DC / AC inverters typically create a lot of Radio Frequency Interference (RFI). Most consumer grade equipment has very little filtering or shielding.

Original Equipment Manufacturer (OEM) Modules 

In some cases the Radio Frequency Interference (RFI) may actually be caused by a module or ground on the vehicle. Depending on the severity of the concern, a dirty ground, improperly built ground shield or module can disable the system. Modules that have microcontrollers using clock circuits to create timing pulses for the microprocessor may radiate Radio Frequency Interference (RFI).

Using Customer Electronics to Pinpoint Radio Frequency Interference 

This method can be a way to determine the cause of a concern well before the sensors and module are replaced with little or no effect on system performance. Since this takes more up front work, it relies on working with the customer to determine what equipment was being used at the time of the event. Question the customer about what kind of devices they are using. Determine which power points are being used and, if necessary, ask that the devices be activated to determine their affect on the TPMS.

Options for Eliminating Intermittent TPMS Operation Caused by Radio Frequency Interference (RFI) 

• If an Original Equipment Manufacturer (OEM) component or customer device is causing the Radio Frequency Interference (RFI) concern, replace the device.
• If a phone charger is causing the Radio Frequency Interference (RFI) concern, the customer should consult with their cell phone provider to acquire a different battery charger.
• If a device such as a dealer installed alarm is causing the Radio Frequency Interference (RFI) concern, move the device to another location in the vehicle. In the case of a portable device move the power cord to another power point location.

In summary, if the Radio Frequency Interference (RFI) source is present and cannot be moved or replaced, the intermittent concern remains. The TPMS must accept the unwanted system operation the Radio Frequency Interference (RFI) can cause.