[SOLVED] Airbag light + other issues + no response from controlunit

M

mMark

Member
Hi all,

I recently encountered some issues with my 2003 BMW E85 3.0 after about 2 weeks not driving the car. The car started without issues, but after a couple of hundred meters the airbag light came on and some other issues started (see below). So far, I have not been able to find the root cause and to fix the problem.

Any help is greatly appreciated!

Symptoms:
- Airbag light came on after driving a short distance
- Turn signals / alarm lights are working, but without the clicking sound
- Electric roof stopped working. I did work when I drove off
- Unable to read any of the safety modules using INPA (Safety Information Module, Sattelite door front L/R, Sattelite B column L/R). The error I am getting here is "IFH-0009: NO RESPONSE FROM CONTROLUNIT. Program will be stopped!"
- In the past I was able to read at least some of these modules: I have cleared an airbag light a couple of years ago after driving without passenger seat. I do recall, however, that I was never able to read all modules (which I think is normal?)​
- It does read the DME/ECU module and some others without issues​
- Other than that the car runs and drives fine

What I have tried so far:
- Changing the battery. When trying to read the modules using INPA soon the battery died. Voltage of the battery was <10V when removed from the car, so installed a brand new and fully charged battery
- Checked the Airbag fuses (2 pcs), which were fine
- Checked the condition of the airbag module under the center console: this was completely dry and no sign of corrosion. Also, the carpet at the B-pillars is dry, but I did not check these modules
- Computer / cable:
- Checked the port settings in device manager (COM Port 1 + latency timer set at 1)​
- Tried to connect with the switch in both settings (so pin 7 and 8 bridged and not bridged)​
- Tried a different K+DCAN cable. Both were relatively cheap (20 - 30 EUR). Blue cable with white PCB and a white cable with green pcb. The blue cable I have used in the past.​
- Tried with two different laptops, both using the USB A port. The software installation, however, was the same for both computers (Mike's Easy BMW Tools).​
​
Any feedback / suggestions are more than welcome!

Best regards, Mark
 
My first thoughts are that the k-bus is getting bad messages on it. See here: https://z4-forum.com/threads/collective-wisdom-needed.152945/#post-2138955

I suspect that this is due to the airbag system, if that's raised a light. If it were me, I'd start by unplugging the airbag ECU, and then trying INPA or ISTA again and seeing if they can communicate with the rest of the car. It could be that unplugging the airbag ECU removes the other issues too like the roof etc.

Good luck!
 
My first suggestion would be, reach through under the coin holder behind the handbrake and unplug the SIM85 (centre airbag module). See if everything else starts working. It is on the k-Bus and if one module on that has an issue it can upset the others. The satellite airbag modules are not on thr k-bus, they report to the SIM85, so it is less likely to be one of them causing the issue.
If the SIM85 has an issue you will not be able to see the satellite modules through it.
 
Thank you both for the swift response and very helpful information :D

enuff_zed said:
My first suggestion would be, reach through under the coin holder behind the handbrake and unplug the SIM85 (centre airbag module). See if everything else starts working. It is on the k-Bus and if one module on that has an issue it can upset the others. The satellite airbag modules are not on thr k-bus, they report to the SIM85, so it is less likely to be one of them causing the issue.
If the SIM85 has an issue you will not be able to see the satellite modules through it.
Click to expand...
This was the easiest to try since I already had removed the center console. When unplugging the center airbag module (SIM85), nothing really changed in the behavior:
- Still no clicking sound for the turn signals. Also, the dash indicator lights and backlight are not working, both with and without the SIM85 connected
- The roof is still not operating. Minor difference now is that the red indicator light is not working at all, which was the case with the SIM85 connected

I will try with INPA to see if it makes any differences in communicating with other modules.

What modules should I be able to communicate with? I recall from playing around in INPA that not all options in INPA are accessible (or available, depending on the options the car has).
Also: the bridging of pin 7 and 8 on the cable: should that be always enabled? Or enabled/disabled depending on the type of module that is accessed? I should probably know, but is has been a while since I had to use INPA...

TriggerFish said:
My first thoughts are that the k-bus is getting bad messages on it. See here: https://z4-forum.com/threads/collective-wisdom-needed.152945/#post-2138955

I suspect that this is due to the airbag system, if that's raised a light. If it were me, I'd start by unplugging the airbag ECU, and then trying INPA or ISTA again and seeing if they can communicate with the rest of the car. It could be that unplugging the airbag ECU removes the other issues too like the roof etc.

Good luck!
Click to expand...
The symptoms described by Scott on the K-Bus trouble shooting guide (copy below) are very similar to what I see. In my opening post I didn't mention anything about the dash lights, but most are indeed also not working. Really helpful guide and I will start doing some measurements tomorrow.
Symptoms: Turn signals work, but, don't display on the instrument cluster, fog light and high beams do not indicate on the instrument cluster, door ajar status does not indicate on the instrument cluster, steering wheel controls for the radio do not work, CD changer doesn't work, radio may say "DISABLED", lights don't flash when locking/unlocking the car, sunroof controls don't work and dash light control does not work on the radio display, instrument cluster display, A/C display and on the steering wheel controls.
Click to expand...
 
Last edited:
Hopefully a few steps closer to the solution:
I measured the K-bus shorting bar and the voltage was around 5 Volts with respect to ground, which is too low as it should be around 12V. I have removed all connectors one by one, until the voltage on the shorting bar was 12 Volts: only one of the connectors pulled it down.

However, still all the symptoms remained the same. No indicator lights on the dash (except for the warning lights), no clicking sound for the turn signals. The roof did work for a moment, but later on stopped working again.

Using INPA I was only able to read the following modules (which is the same as before):
- DME
- DSC
- Electric Power Steering (EPS)
- Instrument Cluster

The Instrument Cluster showed the following errors that inmediately come back after turning off and on of the ignition:
- 135 K-Bus, Kurzschluss gegen Masse. Fehler momentan vorhanden
- 190 Lichtmodul-EEPROM-Fehler. Leitungsunterbrechung. Fehler momentan vorhanden
- 32 Airbag. Fehler momentan vorhanden. K-Bus Telegramm 70h ausgefallen (Maske 10) bei 000000 km

I checked the "faulty" K-bus wire that pulls the voltage down and this is not the wire that goes to the Central Airbag Module (SIM85), the Light Control Module (LCM) or the Roof Module.
Searching for the error codes on the forum led me to the post of Behr in the follwing topic:
https://z4-forum.com/threads/k-bus-instrument-cluster-errors.95901/
Although not all symptoms are the same, it is quite similar and the error codes are exactly the same. However, Fuse45 is still fine and in the correct spot...

Thanks for the great help so far. Any suggestions what to do next..?
 
135 K-Bus, Kurzschluss gegen Masse. Fehler momentan vorhanden
Click to expand...

This one is interesting. Instrument cluster reporting "135 K-Bus, short circuit to ground. Error currently present". So is it your instrument cluster that's causing the k-bus to drop to 5v? You could test by removing the instrument cluster, and checking continuity with a multimeter between the two ends of the k-bus wire.

Now... why is this interesting? You won't see this on INPA, but would if you had ISTA (the INPA replacement, which is slower and not as nice to use IMO), you would see a module tree looking something like this (this is an E46, but the layout will be similar):



bmw-ista-diagnostika-0.jpg

Now, the Kombi is AKA... the instrument cluster! And you can see that is the gateway for the k-bus -> ODB communications! The K-bus will be all the modules on the left, with the black line. The yellow line I think is the can-bus network.

mMark said:
Using INPA I was only able to read the following modules (which is the same as before):
- DME
- DSC
- Electric Power Steering (EPS)
- Instrument Cluster
Click to expand...
The DME, DSC, instrument cluster (and I strongly suspect) the EPS are all on the non-k-bus network.

I am not sure, and it's a semi-educated hunch, but is the k-bus error with your instrument cluster? I'd be tempted to grab a cheap one off eBay, swap it over, and see what changes...
 
Brilliant idea, problem solved! :D

Based on your suggestion, I started by taking out the Instrument Cluster. Easy job, only had to remove 1 screw.
Then I noticed some non-OEM wiring, specifically for the white/red/yellow K-bus wire. In fact, this is something that I have installed 4 years ago for a roof module. This roof module allows remote control of the roof (like the gapTech), but also allows operating the roof while driving up to a certain speed (35, 45 or 55 km/h). Really helpful if you want to close the roof when it starts to rain.

However, it gets the speed information from the Instrument Cluster via the K-bus wire: the roof module is basically wired in between the Instrument Cluster and the shorting bar. When I took out the roof module the voltage over the shorting bar was 12V again and everything worked fine: airbag light was cleared by itself, all dash lights fully working and the K-bus modules are accessible again. Reconnecting the roof module directly gave the same issues as described previously. Clearly the roof module is defective and pulls down the voltage over the shorting bar, hindering communication over the K-bus.

So for those who are checking the shorting bar: if the issues persist when the voltage over the shorting bar is 12V again, please check the Instrument Cluster (or presence of anything that is wired in between... 🫣).

Many thanks all for the great support! I still need to put some interior bits together and will post some photos of the shorting bar location.
 
Yay! Glad you got it fixed - and for free too!

Thanks also for providing the update/closure :)
 
I thought the roof module might be to blame in my case too after seeing your reply as the roof had started playing up immediately before I had these problems (which I'd put down to the car having been sat outside for a while and the roof motor getting wet), but unfortunately the problem persists after disconnecting the roof module.

I've disconnected the instrument cluster and there's no obvious damage/modifications to the wiring etc, does anyone know if there are there any other modules that are connected on the instrument cluster path that would be worth disconnecting/checking, or if it's likely to be the instrument cluster itself that's causing the issue?

I've already disconnected airbag modules/light unit etc but without any success?

Thanks in advance for any suggestions as this one has me tearing my hair out!
 
Dwr2025 said:
I thought the roof module might be to blame in my case too after seeing your reply as the roof had started playing up immediately before I had these problems (which I'd put down to the car having been sat outside for a while and the roof motor getting wet), but unfortunately the problem persists after disconnecting the roof module.

I've disconnected the instrument cluster and there's no obvious damage/modifications to the wiring etc, does anyone know if there are there any other modules that are connected on the instrument cluster path that would be worth disconnecting/checking, or if it's likely to be the instrument cluster itself that's causing the issue?

I've already disconnected airbag modules/light unit etc but without any success?

Thanks in advance for any suggestions as this one has me tearing my hair out!
Click to expand...
Page 16 of this pdf I linked in the thread I linked above


T

Post in thread 'Collective wisdom needed...'

I'd guess k-bus, too.

I had an R53 like this (not quite the same electrical system, but close enough) - the A/C didn't work, the full beam and indicators worked, but the tell-tale lights on the dash didn't work. The radio often said 'disabled', and the instrument cluster lighting didn't work.

For me, it was a problem with the k-bus (the 'rev gauge' above the steering wheel on the Mini). The accepted way to troubleshoot is to isolate each k-bus component on the network one by one, and see when the fault disappeared.

I couldn't get a scanner to connect, as the k-bus was corrupting the...
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