Circuit/System Description

This procedure should be followed for any system malfunction, Service Keyless Start System message, No Remote Detected message, or Key Missing Look For Key message that does not have a DTC present. All of the functions and features of the active and passive keyless entry system, along with the tire pressure monitoring system are tied together through the use of radio frequency to communicate. Determining which features and functions of the systems have failed will suggest what the fault could be and therefore the best diagnostic procedure to follow.

The keyless entry transmitters can only be programmed to one vehicle. They can be programmed more than once but only to the same VIN. Once a keyless entry transmitter is programmed to a vehicle it cannot be programmed to a different vehicle but it can be programmed to the same VIN as much as necessary to complete the diagnostic procedures being followed.

The keyless entry antennas are used as short range low frequency (LF) transmitters. The LF signal is at 125 kHz. High frequencies are also used by the system and they are 315 MHz except for vehicles built to be certified for use in Japan which are 433 MHz. As a vehicle with locked doors is approached with a keyless entry transmitter (remote key) and the exterior door handle/rear closure touch pad is pressed, the keyless entry antenna broadcasts a challenge to the remote key in an approximate one meter range. If the response from the transmitter via radio frequency (RF) is valid, the locked door will be passively unlocked/unlatched and allow the door to be opened.

A low transmitter battery may cause a system malfunction. More often a malfunction is the result of radio frequency (RF) interference from aftermarket devices which could include unexpected items such as nearby flat screen televisions, darkness sensing flood lights, or nearby cell phones. Other more common items that can cause a malfunction are 2-way radios, power inverters, cellular phone chargers, wireless cellular phone chargers, computers, 12 V power outlet USB adapters, etc. High RF traffic areas, such as gas stations which use pay-at-the-pump RF transponders, may also cause interference that could lead to a malfunction.