A passive entry system for a vehicle is provided that includes a vehicle-based communication module mounted in the vehicle and a portable communication device. The vehicle-based communication module includes a transmitter for transmitting a challenge signal to the portable communication device when in a polling state to determine a presence of the portable communication device for allowing access to the vehicle. The portable communication device includes a receiver for receiving the challenge signal and is responsive to the challenge signal when in a response state and non-responsive to the challenge signal when in a non-response state.