What is the reason why the mechanical key cannot lock three doors?

[PrestonLynn]

The reason why the mechanical key cannot lock three doors is: the driver's door and the other three doors do not have a linkage device for the locks. By pressing the lock button on the driver's door and then using the car key to lock the driver's door, all doors can be locked. Keys with keyless entry function will have the mechanical key folded or hidden inside. If it is a conventional folding key, the mechanical key can be accessed by pressing a button, etc., and then inserted into the keyhole. In case the car remote key runs out of power and the door cannot be opened, the spare mechanical key of the car comes into play. Insert the mechanical key directly into the keyhole of the door to open or lock the door.

[ODelaney]

The mechanical key can't lock three doors. I suspect it's due to internal rust or blockage in the lock cylinder. It's common in older cars for rainwater to seep in and accumulate dust, causing the key to get stuck when it can't turn. When checking, don't force it in. First, spray some lubricant like WD-40 and try moving it back and forth to see if it loosens. If that doesn't work, the door lock mechanism, such as the linkage or spring, might be broken and not connecting to the lock, especially in vehicles with frequently used doors. For safety, avoid disassembling it yourself—the internal structure of the door panel is complex, and damaging the trim could be troublesome. It's best to drive to a nearby auto repair shop where they have professional tools to inspect it, usually at a low cost. Regular maintenance can prevent issues—clean the keyhole to avoid dirt buildup, and replace aging keys with OEM parts to save hassle.

[VonIsabel]

I've encountered a similar situation with my car. When the mechanical key couldn't lock all three doors, I suspected it might be due to misaligned door locks or deformed door frames. After a minor collision, the increased door gap caused the latch to not engage properly. First, check if the door is fully closed, then try locking it with the key a few more times. Also, inspect the key for wear - avoid using imprecise duplicate keys if possible. If the issue persists, it could be due to internal components like fatigued springs or loose linkages affecting the entire door linkage system. Safety is paramount, so don't take it lightly. A temporary solution is to securely lock the driver's door and use the remote to lock other doors as theft prevention. Regular maintenance is recommended, including lubricating the lock cylinder to extend its lifespan. If all else fails, consult a reliable technician for repairs.

[DelEmily]

I think the mechanical key can't lock the three doors mostly because of dust accumulation and rust inside the lock cylinder, which is more likely to get clogged during rainy or windy and sandy weather. If the key can't be inserted, don't force it; spraying lubricant like rust inhibitor can solve the problem. Lock block damage is also common, such as insufficient spring tension or disconnection of the linkage rod, requiring replacement of new parts. You can do a simple check yourself to see if the door is tightly closed. If not, go to a repair shop—it's not expensive. Don't ignore it to prevent increasing the risk of car theft.