We park the 308 in the evening, everything works. The next morning, the remote control no longer locks anything. The button on the dashboard still responds, but the key remains silent from a distance. This scenario recurs across all generations of the Peugeot 308, both petrol and HDI, and the failure almost never has a single cause.
12 V Battery Voltage and Central Locking on Peugeot 308
Before disassembling anything, we measure the 12 V battery voltage. On the 308 II and III, the addition of telematics functions (e-call, connected services) has made the central locking system very sensitive to voltage drops. A slightly low voltage is enough to disable remote central locking, without any warning lights illuminating on the dashboard.
Further reading : The latest trends and tips for better managing your personal finances
The engine can start normally with a weak battery, which complicates the diagnosis. Stellantis after-sales networks have also reported a significant increase in preventive battery replacements on the 308 since 2021. If the multimeter shows less than 12.4 V with the engine off, the issue is serious.
To precisely identify the causes of the central locking problem on Peugeot 308, it is also necessary to check the condition of the terminals and the vehicle’s parasitic draw, which can drain the battery in a few days on a recent model parked for a long time.
Related reading : The best strategies for smart investing and growing your capital
BSI Software Bug: The Invisible Failure in Diagnosis
On the restyled 308 II (2017-2020), several Peugeot dealerships have been applying a specific procedure since 2023. Before replacing locks or door actuators, they reprogram the BSI (intelligent service box) and the door control unit.
The reason: energy-saving management bugs cut off the power to the central locking without generating a clear fault in the diagnosis. The vehicle goes into an overly aggressive sleep mode and “forgets” to reactivate the radio reception of the key. This results in a remote that only works when in contact with the lock cylinder, exactly the symptom described by many owners on forums.
This reprogramming is documented in PSA’s Service Box database via internal technical bulletins dated 2022-2023. If the independent garage or dealership directly proposes a lock replacement without having attempted the BSI update, one can legitimately request this preliminary step.
Water Infiltration in the Rear Door Wiring Harnesses
Peugeot issued a service campaign in 2022 targeting certain 308 II models for a water infiltration issue in the electrical wiring of the rear doors. Water rises by capillarity along the wires and causes intermittent central locking failures.
The typical symptom: a rear door that refuses to lock while the other three function, or a locking mechanism that fails in humid weather and works again in dry weather. The failure disappears and then reappears depending on the weather, making diagnosis in the workshop complicated if the vehicle arrives on a sunny day.
- Visually check the condition of the rubber grommets between the body and the rear door, especially on the passenger side
- Look for signs of green oxidation on the connectors of the door harness
- Test the door locking one door at a time with the interior control to isolate the faulty side
Feedback varies on this point: some owners resolve the issue with a simple cleaning and dielectric grease on the connectors, while others must replace the entire harness.
Peugeot 308 Key and Remote: Resetting and Wear
Replacing the battery remains the first reflex, and it makes sense. The classic reset procedure (turn on the ignition, press the lock button for 15 seconds, remove the key) works in most cases of simple desynchronization.
When that is not enough, the problem rarely lies in the key itself. The vehicle’s radio receiver or the BSI module is more often at fault than the remote. A simple test can confirm this: if the key only locks when touching the lock cylinder, it is indeed emitting a signal, but the receiver no longer picks it up from a distance.
On both the 308 THP and HDI versions, the diagnostic procedure remains the same:
- Change the battery (CR1620 or CR2032 depending on the generation) and attempt the reset
- Check the dedicated fuse for central locking in the engine compartment fuse box
- Test with the second key if available, to rule out a remote fault
- If both keys fail at a distance, direct the diagnosis towards the BSI or the receiver
Warranty and Coverage: What Peugeot Covers
Central locking failures related to a software defect or water infiltration in the wiring may fall under the manufacturer’s warranty or a recall campaign. Explicitly ask the after-sales advisor if a technical bulletin exists for the vehicle’s VIN before accepting a quote for parts replacement.
Out of warranty, the bill varies greatly depending on whether the problem is resolved by reprogramming (only labor time) or by replacing the wiring harness and actuator. A serious diagnosis takes time, and troubleshooting is often charged even if the garage finds nothing on the first visit.
On a 308 that has accumulated mileage, the mechanical wear of the lock actuator will also eventually manifest. The internal electric motor strains, then fails. This type of failure is easily distinguished: an abnormal clicking noise is heard in the door at the moment of locking, or the locking works once every two attempts.
The most reliable diagnosis remains one that proceeds by elimination: battery, key battery, fuse, BSI reprogramming, inspection of the wiring, and only then mechanical replacement. Skipping steps often costs more than following them in order.