With the Renault Kadjar there is a persistent problem where the child lock on the rear door switches off automatically while driving. This problem is mainly caused by electronic faults and mainly affects models produced in Spain between 2015 and 2018. Owners report alarming situations in which rear doors unexpectedly open on the motorway, which is a direct safety risk for families with young passengers. This text describes the causes of this fault. You will also find concrete information on how to prevent or resolve this problem.
Why does the child lock on the Renault Kadjar open by itself?
The child lock on the Kadjar sometimes switches off automatically. There are several technical causes behind this. The most common reason is an electronic defect. This defect is often located in the door module. It can also be in the wiring. In many affected models, corrosion develops in the cables. In addition, plug connections can come loose. Vibrations while driving cause the connections to work loose.
There is also something else at play. There is interaction with other electrical systems in the car. Some owners see a link with the engine’s start-stop function. The start-stop function switches off the engine when stationary to save fuel. When the engine restarts, the central locking system is sometimes unintentionally reset. This means that the child lock also switches off. This problem occurs mainly in automatics with keyless entry systems. Keyless entry means that you can unlock and start the car without inserting a key into the ignition.
A weak battery often makes the fault worse. At low battery voltage, temporary errors occur in the electronics. Safety functions such as the child lock then do not operate correctly. Owners particularly notice an increase in these problems during cold periods with frost. Condensation in the fuel tank then plays a role. Battery drain also causes faults.
According to owner experiences, models from 2016 and 2017 are the worst affected. Spanish-built variants in particular are more prone to this defect. Differences in assembly or components used may be the cause. This problem is complex. Electrical wiring, software and mechanical wear all play a role.
Recognisable symptoms of child lock faults
The problem shows itself in different ways. The most alarming symptom is spontaneous unlocking. Rear doors unlock themselves while driving. Passengers can then open the door from the inside. The child lock is activated at that moment. Yet the door opens. This sometimes happens at low speeds, but also on the motorway.
Other owners notice something else. The child lock can be activated manually via the button at the front. After a short time, it switches off again. This happens without warning. Some drivers hear a clicking sound from the rear door. The lock then deactivates itself. In certain models, this is accompanied by the rear windows opening spontaneously.
The following symptoms indicate child lock problems with the Kadjar:
- Rear door unlocks spontaneously while driving
- Child lock deactivates after the engine restarts
- Central locking reacts unpredictably
- Door lock makes unusual clicking noises
- Warning lights on the dashboard relating to door status
How do I repair a child lock fault on the Renault Kadjar?
Disconnect the battery for a quick temporary solution. Disconnect the negative terminal. Wait 10 to 15 minutes. Then reconnect it. This resets the electronics. The fault may be temporarily resolved. Make sure the battery is fully charged. A weak battery causes recurring problems.
Keyless entry systems with flat batteries also sometimes cause door lock faults. The battery is in the keyless card. In that case, press the grey button on the card. The emergency key will then appear. Replace the battery in the keyless card according to the instructions in the manual. This prevents further faults.
Take the following steps for structural solutions:
- Check the wiring to the rear doors for corrosion or damage
- Test the door modules for electronic defects using diagnostic equipment
- Have the dealer check whether any software updates are available
- Clean the door locks and plug connections
- Replace defective cables or modules if necessary
The cost of professional repair ranges between 200 and 500 euros. The exact cost depends on the nature of the defect. In the case of broken cables, the complete door lock often needs to be replaced. The same applies to defective modules. Renault dealers can determine exactly where the defect lies using diagnostics. The diagnosis reveals the precise problem.
Is the child lock problem safe on the Renault Kadjar?
This problem poses a direct safety risk. A rear door that can open while driving puts passengers in mortal danger. Children are particularly at risk. Children are not always aware of the danger. A door blowing open on motorways sometimes leads to serious accidents.
Owners with young children run a serious risk. This problem demands immediate action. The child lock operates unreliably. Driving such a car is irresponsible. Do you notice that a door unlocks while driving? Then pull over safely immediately. Afterwards, contact roadside assistance or a dealer.
Kadjar models from 2015 to 2018 may be covered by recalls. These recalls relate to electrical systems. Locks can also be included in a recall. Ask your dealer whether your car is subject to a recall. Actively check this. Renault offers free repair for known defects. This does not always apply, but it does in a number of cases.
Switch off the start-stop function as a temporary safety measure. Do this especially when you are transporting children. This reduces the risk. The system will then not restart unintentionally. Before every trip, manually check that the child lock is correctly activated. Stay alert to warning lights on the dashboard.
Preventive measures against child lock faults
Regular maintenance prevents problems. Good maintenance significantly reduces the risk of faults. Have the operation of the door locks checked at every major service. Also have the central locking checked. Central locking is the system that locks and unlocks all doors at the same time. Ask specifically about the condition of the wiring to the rear doors. Corrosion often develops unnoticed. This makes targeted inspection necessary.
Keep the battery in good condition. Good condition means that the battery supplies sufficient voltage and remains fully charged. A weak battery is often at the root of electronic faults. Have the battery tested annually. Replace it in good time. Do this especially before winter. Models with start-stop systems need a powerful battery. A well-maintained battery is therefore extra important.
These tips help to prevent faults:
- Clean door locks every six months with contact spray
- Check plug connections for corrosion during wet periods
- Avoid prolonged use of start-stop in the event of electrical problems
- Test the child lock monthly to ensure it is working correctly
- Keep the fuel level above a quarter in cold months
Software updates from Renault improve the system. During a service, the dealer installs the latest software. This software contains improvements for the central locking and door modules. Ask the dealer proactively about updates for your model year. Ask which versions are available.
Real-world experiences from Kadjar owners
Owners share experiences on various forums. These experiences provide insight into the nature and extent of the problem. Several drivers describe situations in which a rear door opened on the motorway. This led to panic. Resetting the battery can temporarily resolve the fault. The problem often returns after a few weeks.
Dealers often find it difficult to reproduce the problem during diagnosis. Various users report this. The defect does not always occur consistently. As a result, the exact cause is difficult to find. This makes solving it even more challenging. Some people choose to replace the entire door module as a preventive measure. This offers peace of mind.
Keyless entry battery problems indirectly lead to child lock faults. International reports confirm this link. A flat battery in the keyless card causes voltage differences. The Kadjar’s electrical system is sensitive to small voltage differences. Small variations cause cascade effects. Cascade effects are faults that spread from one component to other systems. Owner advice recommends having all electrical systems checked in one go. You do this at the first symptoms.
Discover more about the Renault Kadjar
Kadjar owners report more issues than just child lock faults. On the Carnews website, you will find extensive information on other common faults with this model. Timing chain issues occur. Transmission problems are also known. In addition, the site offers practical maintenance tips. This helps to detect and prevent problems at an early stage.
Frequently asked questions
You can recognise a possible defective child lock on your Renault Kadjar if the rear door can be opened from the inside while you believe the child lock is switched on. It is also suspicious if the child locks or rear doors unlock spontaneously while driving or after the engine restarts (for example after start-stop). Sometimes this is accompanied by electrical faults, such as problems with the central locking or other door and window functions. Check whether the problem occurs repeatedly on both rear doors and have the system read out by a dealer if in doubt.
The most common causes of child lock problems with the Renault Kadjar are electrical defects in the wiring or plug connections of the rear doors, often due to moisture or corrosion. In addition, software errors in the link between start-stop, central locking and child lock cause the lock to switch itself off spontaneously. A weakened or poorly charged battery can also cause temporary faults in the child lock system. Finally, mechanical wear or a defective door lock mechanism plays a role in some model years (especially 2015–2018).
You can first check in the menu or at the buttons in the driver’s door whether the electronic child lock is actually switched on and test whether the rear doors can still be opened from the inside. Then manually check the mechanical child locks in the side of the rear doors (small slider or rotary knob) and switch them on and off a few times to rule out sticking. Reset the electrical system by disconnecting the battery for about 10–15 minutes and then test again to see whether the child lock now remains active. If the problem keeps coming back or the rear doors open while driving, use the car as little as possible with children in the back and have the lock and wiring read out and checked by a dealer or specialist.
Yes, regularly check whether the child lock remains switched on after starting and while driving, and test both rear doors separately. Keep the battery in good condition (sufficient charge, replaced in good time) and replace the batteries in keyless entry keys promptly to limit electronic faults. Have the door locks, plug connections and cables at the rear doors periodically checked for moisture, corrosion and wear, and have any software updates carried out by the dealer. Clean and lubricate the mechanical parts of the door locks from time to time to prevent them from sticking or jamming.
On average, the repair costs for a defective child lock/door lock or associated wiring on a Renault Kadjar are around €200–€500, depending on which parts have to be replaced and the labour time. When choosing a garage, look for a clear diagnosis beforehand (for example electrical fault, broken cable, lock mechanism), an itemised quote showing parts and labour, and experience with Renault electronics. Also check whether there is still any manufacturer’s warranty, goodwill or a relevant recall/service bulletin from Renault. For complex electronic problems, it is better to choose a marque dealer or specialist with access to Renault diagnostic software.