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sean, Car and LCV technician
Category: UK Car
Satisfied Customers: 3105
Experience:  UK City & Guilds qualified with 30 years experience
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Air bag error 51 after replacing seats from a 55 into a 04

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I was reading a old answer that applies to me . I have a 04 mondeo tdci 130 and took the interior out of a 55 mondeo tdci 130, now I have air bag light flashing 51, I have replaced the pre tensioners on the seats and found no cracks in wiring. Could I replace the airbag module and airbags from the 55 plate into my car to remove the error 51 or do I have a find seats from the same year as my car to remove the 51 air bag error. Regards David

Hello, sorry I've only just picked the question up, I hope I can assist.

As you've seen previously there are different air bag modules for different year built cars. If the seats are from different year built cars then you can have this fault. As you only have flash code 51 this only relates to the drivers side circuit, flash code 52 is for the passenger side, I would expect this to show as well if the fault were related to swapping the interior.

The wiring pin locations can be different under the seat for different year built cars, check the wiring between pin 13 of the underseat connector (black/red wire) and earth, check the wiring between pin 14 of the underseat connector and pin 25 of the the air bag module large connector. The old connectors and new can plug together but the wiring can go in one side but have no wires on the other side due to the different pin locations.

If the wiring doesn't match these positions then you may struggle as the belt minder systems are different as are the air bag modules as I mentioned earlier. Just confirm the flash codes from the air bag light as well to make sure it isn't showing more than one fault.

I hope this helps but if I can assist further let me know and I'll reply as soon as I'm able to.

Best wishes,


Customer: replied 4 years ago.

May sound sill but you don't have a picture or diagram of which pin is 13, 14 and 25 I having trouble working out which is which.

Hello again,

below is the connector mentioned above, if yours is different let me know the chassis number of the car and I'll get the specific connector.


Best regards,


Customer: replied 4 years ago.



I have been looking under the seat not the airbag module it's self. I'll test with a multi meter when I get back from work.

Hello again,

you are definitely going to have issues as your car was built 10/06/04 so is the earlier type system, the later car that the interior is from is the system that uses the GEM as well as the airbag module for the seat belt, this is the same kind of issue as the question you referred to.

When you swapped the seat belt pretensioners over does the wiring under the seat match the locations for the seat belt wiring? If you fit all the wiring for the old seats up to the underseat connector then you shouldn't have any problem unless you want under seat heating and so on. Also did you check is it just flash code 51 that you've got?

Let me know.


Customer: replied 4 years ago.

The wiring on the seat match up to the way round and fit in fine, to the plugs in the car. The electric up down on the seat work fine. But also noticed that the seatbelt reminder now dosent work either. I still error 51. Airbag light flashes 5-1 times =/

To make life easier I have access to a 03 mondeo I can swap seats with, number WF04XXGBB43930237 would there be any issues with that one.

Hello again,

the seat belt minder won't work correctly as I mentioned earlier cars built up to a certain date have a different set up to later cars, the seat belt minder is connected to the airbag system.

There should be no problem swapping the seats if the other car is an early car but the chassis number you've given isn't valid, where the numbers start there should be a letter after the B4 part not a 3. An 03 registered car should be the early system so should swap straight over with no faults.

Let me know if I can assist further.



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Customer: replied 4 years ago.

Yea i gave up fixing it and swapped the seats out from the 03. All works now. No dowt I will need help again if and when i install heated seats.