Copyright Goodheart-Willcox Co., Inc. 506 Section 5 Electrical and Electronic Systems Technology a corresponding signal is sent to a receiver in the vehicle. The receiver then signals the lock module to activate the door lock solenoids, locking or unlocking the doors. See Figure 38‑3. Many keyless entry systems can also be used to unlock the trunk or power lift gate. Keypad Entry In keypad-type entry systems, the keypad is mounted above the handle on the driver’s door. The keypad usually has five numbers. Pressing the numbers in the correct sequence will instruct the module to unlock the doors. See Figure 38‑4. The driver’s door may also have a key hole for a regular ignition/entry key. Smart Keys Many late-model vehicles are equipped with smart key systems. These systems enable the driver to lock and unlock doors, open the trunk, and start the engine without inserting a key or pushing buttons on a key fob. The smart key system uses proximity sensors that send signals to the ECM to indicate that the fob is nearby. Some systems automatically unlock the doors when the key fob signal is detected, and then lock them when the key fob is moved away from the vehicle. Most vehicles with smart key systems use a push-button ignition switch rather than a key ignition switch. When the key fob sig- nal reaches the ECM, the control module energizes the Headlight relay Hazard light relay Horn relay Control module Door lock motors RR RL P D Door lock control receiver Goodheart-Willcox Publisher Figure 38-3. A remote keyless entry system allows the driver to lock and unlock the vehicle’s doors by simply pressing a button on a key fob. Door lock electronic control Deck lid latch assembly electronic control Fuse panel Keypad actuator assembly Door lock ECM Ignition switch wiring to steering column Power seat connector Switch assembly (trunk) deck lid release Ford Figure 38-4. Some keyless entry systems have a keypad on the outside of the driver’s door. When the number code is entered, electrical signals are sent to the processor. If the correct sequence is pressed, the processor will send current to the door solenoids to unlock the doors.