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Old 23rd May 2020, 17:20   #11
Andy24601
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Default electrical

Okay, so there is no white/red/yellow spots wire going to the head unit. Wirs going to the Head unit are:
red/white
red/green
green/white
black
purple/yellow
grey/green
purple/lilac.
I've unplugged all the wires going to the head unit and that's made no difference
I also have an OEM sat nav thing that is installed above the BCU - unplugging that doesn't seem to make a difference
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Old 23rd May 2020, 19:08   #12
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Default this makes my brain hurt

Bear with me...
So the kbus runs on normal battery voltage (anything above 7 volts). The kbus acts as a trigger wire(?) to various modules. These are wired so that if one stops working then the others still work (individual kbus wire to each module?).
If the power supply is interrupted (maybe some idiot disconnects an earth wire whilst the battery is connected) then the kbus can dump a load of current into the module pcb and then fries the chip.
Logically - everything worked on my car before I disconnected the earth. Once I reconnected the earth then lots of stuff didn't work. So either I haven't connected all the earths up (I'm sure I have) or I've connected an earth that shouldn't be connected (???). Or the kbus has dumped too much current to something (everything?) and killed it dead? Or something else?
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Old 24th May 2020, 11:16   #13
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Default (un)exciting update

So I found a 'how to check your kbus' post on this forum -what you do is:
locate the c0289 kbus header, pull out all the pins bar the LSM, BCU and IPK ones. Switch the ignition to II and put the indicator on and rejoice as the tell-tale on the instrument cluster does its thing. Replace wires/pins one at a time until tell-tale stops - the last wire you replace is the culprit.
So I did all that - even with just the three wires in the tell-tale didn't work, no instruments etc.
So I removed the loop plug from the grey connector and tested each pin for voltage. You get voltage (normal battery voltage) at the BCU and the IPK but not the LMS. I then checked for earths - the only connection to earth was on pin 19 (the one that loops to the LSM). What does this all mean?
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Old 24th May 2020, 11:44   #14
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Take a look at the LSM connector then

Brian
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Old 24th May 2020, 12:00   #15
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Default my ignorance kicking in

Thank you for the advice but without wishing to sound completely stupid, what am I checking for? Am I checking where the multiplug goes into the LSM? If so, there are 53 connections on the plug, am I checking the kbus connection (pin 21)? If so what for, voltage, no voltage? Or am I checking the earths?
I enjoy a learning curve but my 53 year-old brain struggles sometimes, especially with abstract car problems (well, abstract to me). If I can't sort this out then I'm happy to pay someone but there doesn't seem to be anybody local (Southend on Sea).
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Old 24th May 2020, 12:18   #16
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The K-Bus isn't connected to either earth or +12v it is a communication network transmitting data in a series of highs and lows.

If you have a part of the network pulled low, IE permanently earthed, then there can be no data transmission on any part of the network.

It is common, especially if the car has a sunroof, for the LSM to become wet, this can be seen quickly by removing the plug and inspecting the connector, in addition by unplugging the LSM and then seeing if the other items such as windows, central locking, ATC etc work, then either the LSM or the wiring to the LSM need investigation.

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Old 24th May 2020, 12:34   #17
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Default fading fast

I checked the connector to the LSM and it is pristine. I also checked the kbus pin on the connector (10.25 ish volts with a little fluctuation). Both earths fine, 12 volt pins okay. Then I checked if the central locking worked without the LSM plugged in and it doesn't Arrrrrrrrrrrrrrrrrgh!
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Old 24th May 2020, 12:46   #18
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Default

Ok, so it's not the LSM, but we still need to find what is causing the K-Bus network such distress. so if you completely disconnect the header(s), and check each wire individually, what do you see?



Just in case you don't have it, I've included the diagram of the K-bus network.
Attached Images
File Type: jpg K-Bus.jpg (89.0 KB, 51 views)
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Old 24th May 2020, 13:44   #19
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Default kbus

Voltage readings:
Pin 1 (ECU - engine immobilisation) 0 volts
Pin 2 (LSM) 11.64 volts
Pin 3 (IPK) 0 volts
Pin 4 (BCU) 12 volts
Pin 5 (audio Visual) 0 volts
Pin 6 (sun roof/rain sensor) 18 MV
Pin 7 (parking sensor) 13 MV
Pin 8 (linked with pin 9) 0 volts
Pin 10 no pin
Pin 11 ECU seats
Pin 12 no pin
Pin 13 10 MV
Pin 14 10 volts
Pin 15 0 volts
Pin 16 0 volts
Pin 17 30 MV (variable)
Pin 18 0 volts
Pin 19 Earth
Pin 20 not connected
the car has no sunroof and the parking sensors are after-market ones. The head unit is after-market and is disconnected
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Old 25th May 2020, 07:59   #20
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Default I'm done

Right, I consider myself to be a resilient type but this has me beat. Anybody know of anyone nearby that can sort this out for me?(I'm in Southend-on Sea).
There is 'British Legends' a couple of miles away - anyone had any dealings with these people? Or an auto-electrician? As a teacher, I'm classed as a key-worker and so travelling to get my car fixed is probably legit . Help
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