Hello everyone,

I have a 2005 Ford Focus 1.6 Gasoline with an electrical issue in the central locking system. It’s behaving very strangely, as I’ll describe below:

• The doors randomly lock and unlock, whether the car is moving or parked.
• When I lock the car with the key, the turn signal lights don’t flash. However, they do when I unlock it.
• The key only locks the driver’s door.
• Sometimes, the remote key doesn’t work.
• If I try to lock or unlock the doors using the interior switch, nothing happens.

I’ve checked and replaced the fuses related to the central locking system, inspected the wiring that runs through the door, disconnected the battery for about 10 minutes, reset the GEM module using FORScan, replaced the key battery, and tried reprogramming the key—nothing has worked.

When scanning for errors in the modules using FORScan, I found the following error in the GEM module:

• B1300: Fault in the door lock relay coil circuit.

If anyone has any ideas or advice, I’d really appreciate it—I’m starting to go crazy over this.

Thanks in advance!

Does nobody know? 😢

I've no electrical information available for a 2005 Focus, but assuming that it might be similar to later models I would suggest that you need to replace the 'Drivers Door Module' (DDM) located inside of the door.

5 hours ago, unofix said:

No tengo información eléctrica disponible para un Focus 2005, pero asumiendo que podría ser similar a los modelos posteriores, sugeriría que necesita reemplazar el 'Módulo de la puerta del conductor' (DDM) ubicado dentro de la puerta.

Thanks for the response! But if I'm not mistaken, I believe the DDM module controls the power windows and not the central locking system.

It fixed itself last year, but after a year and a few days of heavy rain, it’s happening again….

On 2/14/2025 at 11:49 PM, enrikeco7 said:

Thanks for the response! But if I'm not mistaken, I believe the DDM module controls the power windows and not the central locking system.

Given that the interior switch is dead and you have a B1300 code, the most common fix for this specific Ford era is replacing the Driver’s Door Latch Actuator. If that doesn't solve it, the internal relay in the GEM (fuse box) has likely failed, requiring a replacement module

On 1/30/2026 at 10:52 AM, Eli_P said:

Given that the interior switch is dead and you have a B1300 code, the most common fix for this specific Ford era is replacing the Driver’s Door Latch Actuator. If that doesn't solve it, the internal relay in the GEM (fuse box) has likely failed, requiring a replacement module

I’ve ordered the driver’s door latch actuator and will replace it when it arrives to test if it fixes the issue.

What I find interesting is that the problem only happens during heavy rain, when it’s dry everything works fine, which makes me suspect moisture affecting the actuator or its circuit.

I’ll report back after the replacement. Thanks!

9 minutes ago, enrikeco7 said:

I’ve ordered the driver’s door latch actuator and will replace it when it arrives to test if it fixes the issue.

What I find interesting is that the problem only happens during heavy rain, when it’s dry everything works fine, which makes me suspect moisture affecting the actuator or its circuit.

I’ll report back after the replacement. Thanks!

Interested to hear any updates on this. Its nice to see a fellow MK2 keep plodding on. Not many left in a condition that provides good comfort and reliability.

On 3/2/2026 at 0:33, Eli_P said:

Me interesa saber qué novedades hay al respecto. Es bueno ver que un MK2 como él sigue adelante. No quedan muchos en condiciones que ofrezcan comodidad y fiabilidad.

Finally, I have replaced the driver’s door lock with a new RIDEX unit.

The job took me around 5 hours (I’m not a mechanic), since the door panel, inner metal carrier, and window position all have to be removed and adjusted. It’s definitely not an easy job if you’ve never done it before.

The original FoMoCo lock that I replaced (3M5A R21813 EP) was extremely dirty inside and noticeably damp. There was a lot of dust and clear signs of moisture, which likely explains the erratic locking behaviour I was experiencing. The car used to randomly lock and unlock itself, especially in humid conditions.

After replacing it, that issue has completely disappeared. The locking system is now stable and predictable, and I’m very happy with the result.

There is one difference compared to the original unit:

• Remote central locking works perfectly.

• The key opens the door normally.

• However, the key no longer mechanically locks the door.

When turning the key, the rod and internal linkage move correctly and I can hear mechanical movement, but the latch does not engage into the locked position. It appears that this aftermarket unit does not implement mechanical locking via the key cylinder, only electrical locking via the actuator motor.

Apart from that, everything functions correctly and the “door ajar” status is stable.

For now, I’m going to leave it as it is, since the main problem (random locking) has been resolved and the car locks properly using the remote.

11 hours ago, enrikeco7 said:

For now, I’m going to leave it as it is, since the main problem (random locking) has been resolved and the car locks properly using the remote.

What are you going to do when the battery fails?

4 hours ago, TomsFocus said:

What are you going to do when the battery fails?

If the battery ever fails, in my case it wouldn’t be a major issue.

The mechanical key still works correctly for opening the door, so I would still be able to access the car without any problem.

The only limitation would be that I wouldn’t be able to lock the car mechanically while replacing the battery, since this aftermarket unit doesn’t mechanically engage the latch when locking with the key.

So in a dead battery scenario, the only inconvenience would be not being able to lock the car temporarily during the battery replacement. Apart from that, there are no functional limitations.

You could connect a jump pack and lock the vehicle. Yes/No?

21 hours ago, CARRJ102 said:

You could connect a jump pack and lock the vehicle. Yes/No?

Yes, exactly. If the battery ever dies, I could just connect a jump pack and lock the car normally.

3 minutes ago, enrikeco7 said:

Yes, exactly. If the battery ever dies, I could just connect a jump pack and lock the car normally.

Then the alarm will go off because the bonnet will be open.

Also it won't work if the fob battery dies rather than the car battery.

However, as you can unlock the car manually, that's the most important function. Very strange that your new latch doesn't lock manually, that sounds more like a fault than a function.

16 hours ago, TomsFocus said:

Then the alarm will go off because the bonnet will be open.

Also it won't work if the fob battery dies rather than the car battery.

However, as you can unlock the car manually, that's the most important function. Very strange that your new latch doesn't lock manually, that sounds more like a fault than a function.

Fair points.

Regarding the alarm, I’d just unlock the car before connecting a jump pack, so that shouldn’t really be an issue.

I also keep a spare CR2032 for the fob, so that’s easy to sort if needed.

As for the manual locking, I agree it’s unusual. However, the key turns normally and the linkage moves correctly every time, so it feels more like a simplified design than a defect, especially considering the part only cost around €35 😅

It could technically be a defect, but since the operation is fully consistent and the central locking works perfectly, it seems more likely to be a simplified internal design. Without installing another unit to compare, it’s hard to be 100% certain.

In hindsight, I probably should have gone for a better-quality or OEM replacement to retain full functionality, but at this point it’s done and everything else works perfectly.

15 minutes ago, enrikeco7 said:

Regarding the alarm, I’d just unlock the car before connecting a jump pack, so that shouldn’t really be an issue.

If you lock the car with a jump pack connected then the bonnet would be open and the alarm would go off.

I had a car with a dead battery for a while and was using a jump pack to open the boot to access tools regularly. But then I'd have to go round each door to manually lock individually afterwards. Thought I could cheat it by locking with the jump pack connected, but that just upset the neighbours by setting the alarm off! 🫢