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I bought a s/hand Espace III last year and had this airbag warning syndrome appear shortly after. I did some investigation and fixed my problem (for now at least).
This message gives additional information not mentioned above. [I am an electronics an IT engineer] that is my best understanding of what is happenning.
1. What are the wires connected to:
Airbags contain an explosive charge, which on detonation creates a lot of gas quickly, I don't know the exact speed, but it is in fractions of a second. This gas inflates a bag which cushions the passenger(s) & driver from hitting any hard part of the vehicle. The bag is not sealed, so deflates soon after. The bags are triggered by the Airbag computer when a sensor inside the computer box detects excessive decelleration (i.e you hit something). I addition to the airbags the front two seats include seatbelt tensioners these pull the seatbelts of the driver & front passenger tight when triggered. In the tensioner the explosive is inside a cylinder (a bit like a big bicycle pump); its piston is connected to a rod which pulls the seatbelt tight.
These are EXPLOSIVES and any unexpected triggering is dangerous. The triggering is by a current pulse sents from the airbag computer. The airbag computer contains a small battery charged from the main car battery (?) so that the airbags can still detonate even if a crash disconnecs the main battery. The detonators are similar to detonators used in mining/demolition explosives, I think.
Each front seat, includes a seatbelt tensioner plus an airbag on the back of the seat, to cushion passengers in the second row. A third pair of wires goes to the seatbelt-fastened microswitch on the drivers seat and is unconnected on the passenger seat.
There is another airbag in the steering wheel for the driver and another in the console in front of the front passenger.
2. Why does the Airbag failure signal appear:
Shortly after engine starting and about every 5 minutes or so thereafter, the airbag computer performs a test that ALL its detonators are connected correctly. It does this by passing low voltage, low current electricity through the detonator. This has to be a weak signal to avoid setting the setonator off. If the test current flowing through the detonator is too low or non-existent, the alarm is raised. THe airbag symbol appears in the general purpose portion of the console (usually shows the Radio details) followed by the SERVICE message.
From the display, you as the owner do not know whether the problem is in the detonators in the front two seats or whether it is in the airbags of the steering wheel or front console. If the signal appears you do not know whether or not the airbags will deploy in an accident. A diagnostic computer plugged into the interfface (in the fuse panel undr the front passenger carpet), with renault software, can receive a message saying that the problem is in the seats, but it doesn't say which seat. ( I do not know what other codes are available or whether they can be read with non-Renault software).
Unfortunately the very low voltage/current used for the test is insufficient to overcome even very slight oxidation of the metals in the contacts of the plugs under the seats, so even though the contacts seem to be goldplated, false alarms occur, as we have seen above. Nonethe less you should treat it as a serious alarm until you have proved otherwise.
3. How to fix false alarms.
PRECAUTIONS: disconnect the battery and wait say 5-10 mins, but remember that the airbag computer has its own battery. There is a chance that static electricity might trigger a detonator, so wear only cotton clothes when working on this wiring; no nylon etc. DO NOT USE A CIRCUIT TESTER; the voltage & current of an ordinary ohmmeter or circuit tester are VERY LIKELY to trigger the detonator.
The procedures mentioned above fix a false alarm. Cut and solder is a pretty permanent solution, but your seats will be permanently 'wired' to the car. In my case I used SERVISOL Switch Cleaner Lubricant
and carefully wiped over the contacts with the 'sharp' edge of a cut copper wire (from an old piece of house wiring wire). Then I carefully eased (bent) the connector blades in the sockets so that they would press slightly tighter on the mating part.
4. If the signal persists after cleaning/soldering.
Then your problem was not in the plugs & sockets, it might be in the actual detonators in the seats or it might be in the airbags of the steering wheel or passenger console. I strongly suggest that you go see a garage if the signal persiste.