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.

[VanVivian]

After driving for over a decade, I've found this issue is mostly caused by signal interference. Last time in a mall's underground garage, my car wouldn't lock, and I later discovered it was due to the signal booster on the ceiling. Also, dropping the key might cause a loose solder on the circuit board - opening it up and cleaning the contacts with alcohol can help. Pay attention to the central locking module on the front left door, which controls all locks, as it's prone to failure. If the mechanical key works fine, it's not a problem with the main lock assembly. Charging your phone next to the key can also interfere with the signal - try separating them. Avoid keeping keys with coins or metal objects as they can weaken the signal. During maintenance, ask the technician to check the central locking system's voltage.

[DeBrooklyn]

I've fixed this issue many times. First, rule out basic operational errors: the vehicle must be in Park (P) and all doors properly closed. The remote circuit consists of transmitter and receiver components: depleted key fob batteries are the most common culprit; the vehicle's receiver antenna may have water ingress causing a short circuit, located behind the A-pillar trim; the door lock motor gears could be worn or jammed, visible after removing the door panel; BCM (Body Control Module) failure is the most troublesome, requiring professional diagnostic equipment. For emergencies, use the mechanical key to lock the vehicle and get it checked ASAP. In older vehicles, oxidized wiring can cause poor reception - pay special attention to door lock-related fuses in the fuse box. Keys kept in pants pockets long-term often wear out the micro switches - simply replacing the key fob housing usually solves this.