Airbag Light Error 21 Clock Spring Contact Unit

[ivass]

Hi All,

I have a 99 C4 which I purchased back in 2003. In 2005 the airbag light came on with error 21 – (ignition circuit driver). I changed the clock spring – 996 652 211 00 with the same part number and the problem was fixed. Last year, in November 2012, I got the same issue and purchased a clock spring contact unit – 996 652 211 01 (this number superseded the original part number above) and the issue was fixed again … for about a month! I figured it must have been a defective part and ordered a new one. The new part was installed in January and now, in March, I just got the same error 21 again. What am I doing wrong? There is only one way to connect and install the contact unit and I just can’t figure out what is going on. If replacing the contact unit wasn’t fixing the issue for a while, I would be looking for the problem elsewhere, but it is, so it must be it. Has anyone seen this before?

Thank you,

Ivo

[987_RDC]

Fault codes 04, 05, 20, 21, 36Ignition circuit, driver1. Remove driver's airbag unit.2. Attach the special tool 9516 instead of the airbag unit.3. Clear the fault memory.4. Check whether the fault appears again.a If the fault does not appear again, replace the airbag unit.b If the fault appears again, disconnect plug connection to the contact unit and attach special tool 9516/1.5. Clear the fault memory.6. Check whether the fault appears again.a If the fault does not appear again, replace the contact unit.b If the fault appears again, check the wiring harness for pinches and chafing damage.c If no fault is found on the wiring harness, replace the triggering unit.Proceed as described below to determine whether the fault was eliminated:1. Clear the fault memory.2. Switch oft ignition.3. Remove ignition key.4. Switch on ignition.You may need to borrow the airbag tool (a special resister in box with the correct connector - I think) orfind a shop that has one.

Someone else mentioned it may be possible to "fake" the 9516 tester with a 2.9 ohm resistor. Their logic was that the bag itself has a similar ohm value. Of course disconnect battery and wait 10 min before removing airbag.

[ivass]

Thanks. I will try to isolate the issue using a resistor, but I know that replacing the contact unit yet again will fix the issue … temporarily. It just looks like there is something causing the contact units to fail, and I can’t put my finger on it. When I take the “failed” units, I test them for connectivity on all four wires as I spin the unit from lock to lock and I don’t get any disconnects. However, when I put them in the car I get the error as soon as I turn the steering wheel.

[EleCTriCT]

Just in case,

when Installing a clock spring it usually comes locked in the center position.... You have to make sure that the vehicle steering is in the center position as well. Most are just coiled length of ribbon wire inside and they only have so many turns left to right before you snap/stretch the wiring inside...

you can also adjust the distance of the switch assembly from the back of the steering wheel, there is usually a small pinch bolt (8mm head) on the underside. Maybe its getting "crushed" when you bolt the wheel on etc....