05-29-2014, 11:05 AM
Join Date: May 2014
Airbag light on / horn not working
Just to document my findings, perhaps useful for someone else!
Disclaimer: working on airbag components can be dangerous. I cannot take any responsibility for errors made. When in doubt, consult your dealer.
Problem: on my Jimny 2000 JLX, the Airbag SRS light burns and the horn does not work anymore.
Cause: the 'steering wheel coil' is defective. This coil is mounted in the steering wheel and provides the electrical connection from the steering wheel airbag and the horn contact to the rest of the car.
Root cause: when installing the coil one has to make sure it is in the 'center' position. The coil can only take a limited number of turns left or right and you must make sure that the coil is in its middle/center position. This to ensure that it can take the full number of steering wheel turns left or right. If not, you will damage the coil (after replacement, I opened the defective coil which makes very clear what has gone wrong. The 'wire' inside the coil is much like the spring in a mechanical alarm clock).
To fix it, you need to replace the coil. In my case, the official spare part is a complete assembly of all the steering wheel switches, hazard switch and coil. It is hugely expensive. I obtained a second hand one, just the coil. The coil can be easily separated from the steering wheel switch assembly.
- Please ensure you are informed about working with airbag components!
- Disconnect battery and wait 30 mins
- Remove the steering wheel:
.. pry off the square cover at left side (there is no cover on the other side)
.. use a suitable torx to remove screws left and right
.. remove the plastic part holding the torx on left side
- remove the airbag:
.. move the airbag unit partially from the steering wheel, just enough to expose the connectors
.. open/disconnect the yellow airbag connector and the connector for the horn. Airbag connectors typically have a 'safety catch', so opening is bit more tricky
.. place the airbag unit aside
- remove steering wheel:
.. loosen - but do not remove - center steering wheel nut
.. remove the steering wheel (this can be a challenge, some suggest to hit the steering wheel on left/right/top/bottom until it comes of. I used a cheap steering wheel puller.
.. remove the center nut completely and remove the steering wheel
- remove bottom part of steering house cover (3 screws) and a few catches
- remove top part of steering house cover
- open the yellow connector from the coil to the car
- disconnect the larger wire steering wheel switch connector and pry-out the horn contact wire from steering wheel switch connector (or simply cut it and fix the wire later to the new coil) (At this point I also took out the steering wheel switch assembly and pried out the pin from the horn contact at a more convenient location)
- remove the 4 screws of the coil
- remove the coil:
.. once completely removed, you can safely check for any open connections (*)
- replace with the known good coil, steps in reverse order
After reconnecting the battery and turning on the ignition, the airbag SRS light performed its normal flash routine and did not light up anymore. There was no need to reset the airbag control unit. Also the horn was working again.
(*) Warning: do not perform ANY measurement on the airbag system unless you know exactly how & what; in my case I only measured the coil after having completely removed it the from the car. Take utmost care when working on airbag components, follow official instructions please. You really do not want the airbag to activate while working on it!!