Why can the remote key unlock but not lock the car door?

[EmiliaMarie]

First, check whether the indicator light on the remote flashes when unlocking. If it doesn't flash, the issue lies with the remote itself. If it flashes but the vehicle's central control shows no response, troubleshoot the central locking system's unlocking circuit accordingly. The basic components of a remote key consist of the following two parts: 1. Transmitter: Composed of a transmission switch, transmission antenna, integrated circuit, etc., containing an identification code storage circuit and amplitude modulation circuit, with a button-type lithium battery installed on the opposite side of the circuit. The transmission frequency uses radio waves, sending a signal once per press of the transmission switch button. 2. Receiver: After the transmitter sends the identification code via shortwave modulation, it is received by the vehicle's shortwave antenna, then enters the receiver's electronic control unit through a distributor for demodulation via a shortwave high-frequency amplification processor, and is compared with the demodulator's identification code.

[LaDavid]

I've encountered this situation before—it's really annoying when you can unlock but can't lock the car doors. Usually, it's because the key fob battery is running low, and the signal strength isn't strong enough to perform complex operations. I recommend trying a new coin cell battery first; they're available at any supermarket. If the car door isn't closed properly, it might not lock either—especially the trunk, which is often overlooked. Another possibility is interference from nearby cell towers or high-power electrical devices; try moving a few steps away and locking the car again. Sometimes, the remote key buttons have poor contact, so try pressing them multiple times from different angles. Lastly, it could be due to aging or stuck door lock motors, which would require a visit to the repair shop. Remember to regularly check if the key's waterproof case is damaged, as dropping it in water could cause an internal short circuit.