Airbag/seat belt Light Diagnosis

[Three Syllables]

Hello there!

I was casually reaching around under my seat one day to find some change for a car park ticket machine, and on came the dreaded 'airbag / seat belt light'.

It's now MOT time and I've been trying a few different ways to clear this light, assuming that there isn't an actual fault in the cabling etc, as I've taken both seats out and can't spot any points where the cable/plug may have failed, but if anyone has been through this and could advise where I look closer, I'd be all ears.

So, I've tried a mobile mechanic friend who brought a rather expensive bit of bluetooth obd connectivity, and our own RobertT who lives locally had a go with his laptop and both have come back with the same issue when trying to clear the codes:

" [ERROR_ECU_REJECTED] " or something similar,

I can read all the other parts of the car, I can read that its finding a fault in both sides of the pre tensioner (I disconnected them with the battery still connected when I removed the seats) but when I try to reset the codes, it displays that message.

So, I've bought a B800 tool online, wondering if a more direct bit of kit will solve the problem... it didn't but here's the codes it shows in order.

FA (then enter)
38 (control unit fault, swinging voltage test)
02 (is this referring to the table?)
03 (is this referring to the table?)
F0 (if this is from the Table 40 codes, its (Control unit fault, internal error)... but I'm not sure?)

Trying to clear the codes using 'cA' results in '--' and nothing happens on the dash.

************************************************
... can you help?

I've been reading around, and I've found that replacement airbag modules are required if the ECU REJECTED error is reported, and that seems to correlate with what my shiny new B800 is reading, that the control unit is faulty.

Do you know where I can find the airbag module? I believe its under the centre console, does anyone have any pictures?
Do I need to match the model/part numbers with my existing module for this to work?

My MOT is due on Aug 19th and I'm trying in desperation to get this sorted asap, any help would be appreciated.


Chris
2000 Z3 2.0 in Aegean Blue

[Hairyscreech]

This is a similar issue to my airbag light but I have not dug into mine yet.

I believe the Z3 is not fully OBD2, do you have a round 20pin connector under the bonnet?

If so your issue may be that you need an ADS connection to that plug to fully access the ABS unit.

[BladeRunner919]

This is a similar issue to my airbag light but I have not dug into mine yet.

I believe the Z3 is not fully OBD2, do you have a round 20pin connector under the bonnet?

If so your issue may be that you need an ADS connection to that plug to fully access the ABS unit.

He's used all the correct diagnostics and even had RobertT have a look with his diagnostics. It's not a connectivity issue from the point of view of having the wrong equipment, it's clearly a problem with either the ECU or potentially the wiring between the ECU and the communications port.

[pingu]

Hello there!

I was casually reaching around under my seat one day to find some change for a car park ticket machine, and on came the dreaded 'airbag / seat belt light'.

It's now MOT time and I've been trying a few different ways to clear this light, assuming that there isn't an actual fault in the cabling etc, as I've taken both seats out and can't spot any points where the cable/plug may have failed, but if anyone has been through this and could advise where I look closer, I'd be all ears.

So, I've tried a mobile mechanic friend who brought a rather expensive bit of bluetooth obd connectivity, and our own RobertT who lives locally had a go with his laptop and both have come back with the same issue when trying to clear the codes:

" [ERROR_ECU_REJECTED] " or something similar,

I can read all the other parts of the car, I can read that its finding a fault in both sides of the pre tensioner (I disconnected them with the battery still connected when I removed the seats) but when I try to reset the codes, it displays that message.

So, I've bought a B800 tool online, wondering if a more direct bit of kit will solve the problem... it didn't but here's the codes it shows in order.

FA (then enter)
38 (control unit fault, swinging voltage test)
02 (is this referring to the table?)
03 (is this referring to the table?)
F0 (if this is from the Table 40 codes, its (Control unit fault, internal error)... but I'm not sure?)

Trying to clear the codes using 'cA' results in '--' and nothing happens on the dash.

************************************************
... can you help?

I've been reading around, and I've found that replacement airbag modules are required if the ECU REJECTED error is reported, and that seems to correlate with what my shiny new B800 is reading, that the control unit is faulty.

Do you know where I can find the airbag module? I believe its under the centre console, does anyone have any pictures?
Do I need to match the model/part numbers with my existing module for this to work?

My MOT is due on Aug 19th and I'm trying in desperation to get this sorted asap, any help would be appreciated.


Chris
2000 Z3 2.0 in Aegean Blue

After selecting FA and pressing the ENTER button, the first code is the Table, so

38 - is the Table (page 8 in my book)

then you selected SCROLL and got the first error code

02 - there is no 02 in my book, but 2 is "warn lamp"

then you pressed SCROLL and got the next error code

03 - again there is no 03 in my book, but 3 is "supply voltage"

then you pressed SCROLL and got the next error code

F0 - again, there is no F0 in my book in Table 38, but there is 0F "firing circuit, passenger airbag, stage 2"



Given that you said, the fault happened just after you reached under your seat, I think that you disturbed the wires there and that it would be safe to clear the codes.

Connect the device, scroll to CA and select ENTER. Let the machine do its stuff and repeat the process two or three times as it may take several attempts to actually clear the codes.

[Robert T]

Hi Chris. Sorry to hear that you still haven't managed to resolve this.

As stated, we ran INPA on my laptop connected via the round 20 pin connector under the bonnet (this is the only way to talk to the airbag module on the Z3). The car is a facelift, so has the more modern electronics that my USB cable requires. Whilst we could read all data and the error codes from the airbag module, attempting to clear the errors resulted in the message:

Code: Select all

ApiCheckJobStatus: Job-Status error: [ERROR_ECU_REJECTED] instead of [OKAY]!

The errors we read were:

Code: Select all

240   Interner Steuergeraetefehler (Internal Control unit error)
Error frequency : 62

3     Zuendkreis ZK2 -> Gurtstrammer Beifahrer (Ignition circuit ZK2 -> Belt tensioner passenger)
Error frequency : 1
    Fehler zur Zeit nicht activ (Error currently not active)
    Widerstand zu gross (Resistance too high)
    Fehler ist nicht sporadisch (Error is not sporadic)

2     Zuendkreis ZK1 -> Gurtstrammer Fahrer (Ignition circuit ZK1 -> belt tensioner driver)
Error frequency : 3
    Fehler zur Zeit nicht activ
    Widerstand zu gross
    Fehler ist nicht sporadisch

This would correspond to the 02, 03 and F0 (240 in hex). It looks like the Internal Control unit error is preventing the codes being cleared and if the messages are to be believed the errors 2 and 3 have cleared (not currently active).

From the other diagnostics I did, the part number for the airbag control module is 8386192, built week 10 of 2000 and coded on 05/05/2000. The part number is only the last 7-digits and the full part number is likely to be 65.77.8.386.192, which has now been superseded by another part (see http://bmwfans.info/parts-catalog/65776908896/). I would also check the part number on the unit itself, as it is an expensive item if you get the wrong one. They do have to be coded to the car, so it would be worth getting one off a car with identical airbag setup to yours (the implication on bmwfans is that this module is the same for cars with and without side-airbags).

Cheers R.

[pingu]

Code: Select all

ApiCheckJobStatus: Job-Status error: [ERROR_ECU_REJECTED] instead of [OKAY]!

The errors we read were:

Code: Select all

240   Interner Steuergeraetefehler (Internal Control unit error)
Error frequency : 62

3     Zuendkreis ZK2 -> Gurtstrammer Beifahrer (Ignition circuit ZK2 -> Belt tensioner passenger)
Error frequency : 1
    Fehler zur Zeit nicht activ (Error currently not active)
    Widerstand zu gross (Resistance too high)
    Fehler ist nicht sporadisch (Error is not sporadic)

2     Zuendkreis ZK1 -> Gurtstrammer Fahrer (Ignition circuit ZK1 -> belt tensioner driver)
Error frequency : 3
    Fehler zur Zeit nicht activ
    Widerstand zu gross
    Fehler ist nicht sporadisch

These are the error codes from Table 40 of the B800, not Table 38. Now, I'm a wee bit confused

[Three Syllables]

I've managed to source a replacement AIrbag Module with matching part number etc.

Hopefully it arrives this week, I'll swap them over and give the B800 another try and see if it has any luck.

Fingers Crossed

[Three Syllables]

Update:

My car is in pieces (centre console removed) and I'm just as confused as ever, so upsetting.

I bought a replacement control unit on ebay (wasn't cheap) which matched the unit in my car exactly.

I've just taken the centre console out (gosh I hope I can put it back together again) to access the unit and removed it.

upon reconnecting the battery, the light is still showing, so I've proceeded with the B800 which doesn't seem any help:

Current codes are:

38 (table)
1b (Child seat detector)
F0 (still not sure)

... after several reset attempts, nothing has changed. So I started playing with the fuses (41 and 42 for 'airbag' in the fusebox cover) and now the codes are

38 (table)
1b (Child seat detector)
F0 (still not sure)
1A (Seat occupancy detector; coding data)

and I can't clear that now.

When plugging in my old airbag module, its still displaying the same codes as before.

I have no idea what to do

[Three Syllables]

or. If like with the other module, it's actually NOT table 38 like it says, and it's actually table 40. then it would be:

1b (crash telegram memory)
F0 (control unit fault, internal error)
1A (Seat occupied recognition 1 (SBE1)

... gosh, I feel helpless here heh.

[Robert T]

Well that's disappointing, Chris. It was looking like your control unit was at fault, but I can't see two units having exactly the same problem. It could possibly be the wiring or connector, and the module is not getting all the signals it needs?

F0 was one of the codes that I read - internal error.

Looking back at some of the other cars I've checked, I can fine one of your other codes:

1A (26) = Sitzbelegungserkennung 1 (SBE1) = Seat occupancy recognition 1 (SBE 1)

We need some more detail on what can cause the internal error (F0) code. Fix that and you should be able to clear the errors.

Best regards,

Robert

[littlefeller]

don't know if this is valid on the z but this is what I have found out (the hard way) on other cars. the problem with airbag ecu is they don't forget, if it fires a bag or belt tensioner you cant simply reset it, it can only be cleared by wiping the memory and this has to be done professionally. it may be the second ecu you have brought came from a crashed car, in which case it too wont forget. I have a similar issue now with a 206 that a deer decided to commit suicide against and set off the passenger seat belt personally I cant see how the original ecu thinks that it has fired something if all you were doing was scrabbling around under the seat, have you checked the tensioners, are they both the same length ie has one fired at some point without you knowing? do you have an airbag switch for the passenger side? if yes ignore this question.

[Three Syllables]

Its more to do with it losing connection momentarily because the cable loom was poorly designed, I've read just about every post on the subject across multiple forums and it's a lot more common than you would think.

Clearing the codes with INPA etc should rewrite the memory to allow them to fail again if the problem still exists. There is no problem with my seat belt tensioners as they didn't show as a code on the second unit - the reason the 2nd unit didn't work was the 2nd unit also suffers from a f0 control unit error which is preventing the memory from being rewritten or cleared...

... The unit I've bought was knackered, basically - it seems I was lied to by the seller and he's now fully refunded me after I explained many of the points made in this post, which was kind of him. So far as I can tell from his history/feedback, he may have bought a new unit a few months ago and this was perhaps his old one he's selling, but it didn't work out as I was able to prove it was showing codes not from my car, He asked me to throw it in the bin, which I shall.

So the search continues for a replacement unit, i'm confident with a good unit it will clear the codes and we'll be back in business

(crosses fingers for another 8386192 to appear)

[Brian H]

…….(crosses fingers for another 8386192 to appear)

There is a member on here, spurs fan in a coupe, he breaks Zeds of all shapes and sizes, maybe send him a PM to see if he has one?

[Three Syllables]

hehe! I sent him a PM yesterday as I found a photo he took of him having one in possession! it's gone now sadly...