P38A airbag fault ...

So it has finally stopped raining, or at least steady spots and warmish which is equivalent to a Lancastrian summer so I decided to investigate my Airbag Fault message from last year on my 1995 diesel.

Nanocom says bulb open circuit which sounds simple but both bulbs work fine in their little capsules when removed and tested on the bench.

Next stop, the cluster itself. The blue plug bottom left as you look at it has 5 pins which I will call 1-5 left to right. Pin 1 has a green wire, pin 3 a purple wire and pin 5 a grey wire. On the back of the instrument cluster the top bulb is called SRS1 and the bottom bulb SRS2. The right-hand contact for bulb holder SRS1 is connected to pin 3 and the right-hand contact for bulb holder SRS2 is connected to pin 5. The left-hand contact for the bulb holder of both SRS1 and 2 connect to pin 2 which has no wire!

Anyone know if this makes sense?

If it does make sense, any idea where next to look for a break?!

Put bulbs back in and no continuity to pin 5! Bent copper tangs on bulb holder for SRS2 out slightly and continuity between pin 2 and 5 restored and pins 2 and 3 still show continuity. Reassembled and lo and behold, Airbag Fault.

B*st*rd.

Ah, hang on. Cleared fault with Nanocom and it hasn't returned. Previously it returned after approximately 10 seconds. Fingers crossed!

Grrrrrr said:

Ah, hang on. Cleared fault with Nanocom and it hasn't returned. Previously it returned after approximately 10 seconds. Fingers crossed!

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Don't forget the toes aswell, got all mine crossed for you

What about the clock spring behind the steering wheel?
Could be a dirty spot on the ring circuit.
I've à client who brought a mercs A180,
It kept speed limiting at 120kmh.
He had an airbag fault, no esp, no abs and no controls on the steering wheel. (couldn't turn the limiter off)
The steering angle sensor had no reply for the diagnostics either... Dead clock spring... Or yours could be a faulty airbag after 20+ years maybe?



Or a sh*tty bulb...

So you moved them about a bit and now it works?

RangeRoller dt said:

So you moved them about a bit and now it works?

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Each bulb is held in a little plastic capsule that screws in with maybe a quarter turn. Took capsule out and you'll see a copper lug each side which makes contact with the board. I bent the tangs or lugs forward a bit and replaced.

@Mark: before I started the rotary coupler was my first thought, as much as anything because the message came up after I wrenched the steering wheel across avoiding a prick-merchant barrelling down a country road. The Nanocom said otherwise!

Grrrrrr said:

Each bulb is held in a little plastic capsule that screws in with maybe a quarter turn. Took capsule out and you'll see a copper lug each side which makes contact with the board. I bent the tangs or lugs forward a bit and replaced.

@Mark: before I started the rotary coupler was my first thought, as much as anything because the message came up after I wrenched the steering wheel across avoiding a prick-merchant barrelling down a country road. The Nanocom said otherwise!

Click to expand...

Sh*tty bulb