Had a problem with my passenger seat buckle recognition switch a few times after accidentally dropping my tool box between the two front seats. Unfortunately the heavy tool box fits well but can catch the seat buckle latch and makes it flex 90 to 120 degrees outward (away from the seat). Let just say it happened more than once! So after visiting the dealership and getting it replaced (twice) under new car warranty :->, I encountered the problem again (surprised!). I decided to fix it myself as a new part (# 639 860 00 69) is out of the question ( $120 AUD ) and upwards of $70AUD for a second hand. I quickly located the problem within the cable going to the internal switch and no real issue with the mechanics of the latch or switch itself. See below.


Ebay - Viano/Vito Seat Buckle stalk

I think the main issue is that the cable has a mechanical strain relief that "cuts into" the cable (2 wires) when it’s flexed excessively/repeatedly. (I've read owners with "larger" backsides have had similar issues with the seat latch being flexed).


Typical seat belt buckle latch stalk

To fix the issue is not so easy. Many of the forums say to 'just place a 100 Ohm resistor across the wires" and its fixed. However this might trick the SRS into thinking that someone is in the seat and set off the airbag/pre-tensioners in the unlikely event of an accident. The best fix I've implemented is to remove the seat stalk cover (flips off) and undo the 17mm blot holding the stalk to the seat. Unplug the cable from its connector , which is located under the seat (I undid all connectors under the seat to be sure i didn't "zap" the SRS computer). Then open a small area of the back-shell to expose the wire/resistor combination (don’t try opening the seat buckle latch backshell completely, it will destroy the seats stalk and latch). Then solder directly to the copper contacts inside the stalk switch. However if you have damaged the SMD resistors you will need to replace them to. I quick look on the internet shows that the wires have 400 ohm resistance all the time that drops to 100 Ohm when the buckle is inserted into the stalk latch.

I visit to the local tech store for 2 resistor (100 Ohm and 270 Ohm) and I coupled together a simple fix using the following circuit.


100 Ohm 270 Ohm

Yellow wire ----- /\/\/\/\/--------contact 1 ----/\/\/\/\/---- contact 2--------- Blue Wire


See below. (You need a fine tip soldering iron/solder and wire cutters)

Repair inside backshell
Be sure to insulate the wires / resistors from each other and from the metal inside the stalk/buckle latch. I used hot glue to good effect..
Testing doesn't require any error codes to be reset. mine started working as soon as i re tightened the bolt and pushed all the connectors back together.

Hot Glue.... good insulator...

 

Hello
I had the same problem in my Viano W639 and I solved it. As a result, I've done an interesting video (sorry, at his moment is in Spanish) and I think it's self-explanatory.
I've to point that in the W639 the resistors are 100 Ohms and 300 Ohms exactly.
See video: Schematics also can be found in my blog: repairing seat belt buckle switch in Viano W639
I hope you find it useful

 

What is wrong with that? I have a 2016 Vito at work, and are regularly having trouble with the seat belt alarm. (I'm ALWAYS buckled up when driving, so no worry about that) On my car, only the driver's seat is installed with a belt alarm. I don't understand. What are the disadvantages? There will always be someone using the drivers seat while the vehicle is moving forward

Sorry for bringing a old thread up, but I'm curious.

 

Thanks for reading. Its good to know its still of relevance as these cars get older. I see in the case you described with your W639 Vito (if correct) that it won't make much difference if its the drivers seat belt sensor is overridden or the SRS is not on. Not sure of your exact model Vito but I'd double check if I was you, just in case (that the passenger seat belt sensor isn't fitted. or check your option card for

• J56 SEAT BELT WARN. SYS. F. DRIVER + FRONT PASS. SEAT).

With the W639 Viano the SRS light will switch on at some stage and stay on. This may only apply to cars with front passenger seat occupancy sensor and the seat belt pretensioners (Which the 2011 Viano 639 have std.). These sensors work to trigger both the passenger air bag and passenger seatbelt pretensioners. Like you said, if its just you in the car/van then then your safer in an accident and its just an increased cost of repair for the 639 Viano right? (new air bags, new dash, new seatbelts + the damage to the car etc). If its under insurance it wont cost you any more I expect (unless it increases the cost of repair and your van becomes an un-economical repair). If an SRS light is on the system could work regardless or not. If my child rides in the front seat (or someone less than 45 Kgs) then the air bag and pre-tensioners will deploy (or might not deploy correctly depending if the belt is worn or not) that can be a safety issue that ends badly for the passenger. Safety First!

 

Well Done.

 

Well done.