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Auto Airbag System Repair/VW polo airbag warning light


I bought a VW polo 2001 1L in April last year.. The engine had been replaced with one from a Seat also 1L.
When I took it for its car test recently it failed because the airbag warning light did not go off independantly, it had been wired to the check engine light. When the mechanic connected his computer he couldnt get into the airbag system and so replaced the ECU with a 2nd hand one. On taking off the dash he found that the clocks had been drilled into and resistors added to the wiring. The unit then came up with a fault in the steering wheel sensor which he also replaced with a 2nd hand one. and then he replaced the clocks with 2nd hand ones. At this point the car went to an auto electrician who went through all the wiring and couldnt find fault. The car went to a 2nd mechanic who replaced original ECU and clocks and reprogrammed but the light wont go off. Could this be anything to do with the changed engine? and why had resistors been added? In every other way its a great wee car but it needs to pass its test....

ANSWER: Hello Liz:

Sorry about your vehicle.  I'm afraid I don't have good news for you...
The problem is that VW uses very specific components for their electronics in the airbag system.  You cannot take one from a 2nd hand car and combine it with components from another 2nd hand car and hope they will talk to your vehicle's computer.  They won't.  And that is why your airbag light is on.  These components need to be programmed to your specific VIN and need to b new form the dealer (expensive as it may be).
Regarding the resister, it would appear that the previous owner opted to bypass the airbag altogether and tried to trick the computer into thinking the airbag (with the correct resistance) was installed.  Once again, this is not the correct repair and needs to be eliminted and corrected with the proper components.
You may find the cost of repairing this system is greater than the value of the car, which may be why it was such a deal in the first place.
I'm sorry to tell you these things, but as your family's safety is at risk, you need to know what to do.

I wish you well and good luck, but I would take it to a dealer and get an estimate for repairing it completely and correctly, then decide if it's worth fixing and keeping


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QUESTION: Thanks for your reply Doug.

As an afterthought...
Can I replace one component of the system ie just the ECU if that is the problem, or do I need to replace everything that connects to the ECU as well?


Originally, the Airbag Control Unit should have been replaced with a new one.  Subsequent to that it sounded like other components were also swapped out.  Those in turn would need to replaced with original equipment new if that was the case.  Once everything is installed, the ECU will then need to be programmed to your vehicle Id number and that should do it  

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Douglas Gan


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