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Hi everyone,

Just discovered the dreaded air bag light on the dash on the morning of my cars MOT, BMW Z4 2003 2.5i
Managed to complete a diagnostic check to identify the following two fault codes:

9851 Control Unit Fault - Permanent
9853 Short circuit, firing circuit, front airbag, left, active head restraint, front right (E6x), to positive - Intermittent

I am guessing that the 9851 code has been triggered by the short circuit fault, unfortunately I no idea where to start with this?

I have managed to locate the air bag module to get the part numbers: 65.77-6935920 & BMW Nr 31693592001B
Contacted several air bag services including crashdata and they do not provide a reset service for this module

Any advice or help with this would be much appreciated

I had to replace my satellite module recently due to water damage. Not sure if that’s the route you need to go, if it is short circuiting could it be an issue with a damaged cable?

If you do need to replace it you can use eBay and realoem to find a replacement module and then code your vin. TomR has a thread and I recently documented how I did it in this section of the forum.

Before fitting the replacement main module with battery disconnected check out all the wiring connections under the seats and clean them with electrical contact cleaner, check for damaged wires. The replacement module should be the same part number as the old failed one however if you check Realoem you will find it will list modules that are compatable they are listed as being compatable retrospectively or not in the listing. Here is the Realoem link to a 2003 2.5 airbag system page showing the list, I searched this using my chassis number as my car is also a 2003 2.5. The relevant pages are in the Audio,Navigation and Electronic Systems section. https://www.realoem.com/bmw/enUS/part?i ... 5776935920
The replacement module will need coding to the car using NCS Expert software on a laptop.
Only ever changed a main module on a Z3 so not done a Z4 but the method will be the same.
You have to be careful what you buy as if the module has come from a crashed car the module is locked up and has to be fixed internally on the circuit board by the likes of Crash Data companies.

Thank you for the replies, I appreciate these. Have just returned from hols and I have just managed to locate a replacement module (same original part number) that is from a dry / non-accident vehicle.
I will check the connections under both seats and apply some WD40 contact cleaner. I had both seats out to totally clean and dry out the carpets in June, maybe this upset something. I'll also inspect the faulty module as soon as I can get it out.
I have never coded a unit, is the NCS Expert software readily available?

SB73 wrote: ↑Fri Sep 02, 2022 11:21 am Thank you for the replies, I appreciate these. Have just returned from hols and I have just managed to locate a replacement module (same original part number) that is from a dry / non-accident vehicle.
I will check the connections under both seats and apply some WD40 contact cleaner. I had both seats out to totally clean and dry out the carpets in June, maybe this upset something. I'll also inspect the faulty module as soon as I can get it out.
I have never coded a unit, is the NCS Expert software readily available?

Check my post, I found the software on bimmerscene.

viewtopic.php?t=136703

So finally got the air bag module out the car yesterday. No visible sign or evidence of water on the unit - connectors all appear to be in tact.
Battery needs replacing on the car as it no longer holds charge (has gone flat for the third time)....
Could it be possible that the battery failure has caused the air bag lights to trip?

Further update on my air bag light journey..... I had both codes removed from the main air bag module located under the centre console.
Air bag light is still on with the 9851 code and the error:
SBSL: Satelit B-pillar left side
SBSL: Control-unit fault
Permanent

I have located and removed this unit (65.77-6933985) - it appears to be dry and intact with no water ingress.
I've got the part number supersession of realoem - i'm wondering if these units need to be coded or are they plug & play sensors?

Satelite modules need coding to the car same for main central module, they need the Vin number of the car in them so that they can all talk to each other. NCS Expert will code the modules.