MELISCAT
Member Since: 17 Dec 2009
Location: Macclesfield, Cheshire
Posts: 132
  
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| Discovery 3 MOST Bus diagram |
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HI, does anyone have a diagram for the MOST Bus layout of the Disco 3 fitted with the Harman Kardon Logic 7 premium system?
I am having an issue that may be resolved by performing a HARD Reset of the cars ECU's (Screen Stuck on logo and no audio. Diagnostics say that the Audio Amplifier and Traffic Management modules are not communicating with the ECU's).
I would like to know which units of the info system are part of the MOST Bus. I suspect that the Sat Nav unit is directly connected to the screen for video,
Any help would be appreciated.
Thanks
Mike Mike
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 6th Oct 2019 5:18 pm |
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Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10361
 
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it's all in series.
headunit
display
amp
tms (in rear)
and back again to headunit
you can unplug the suspect unit (and then joint the 2 ends together with a plug loop) or even biro case!
and see if things start working
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| 6th Oct 2019 5:37 pm |
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MELISCAT
Member Since: 17 Dec 2009
Location: Macclesfield, Cheshire
Posts: 132
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Thanks Pete, do you know if the TMS unit is behind the roof lining or is it on one side of the load bed?
Mike Mike
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| 6th Oct 2019 9:37 pm |
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Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10361
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On the drivers / right side on my RRS
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| 7th Oct 2019 10:50 am |
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MELISCAT
Member Since: 17 Dec 2009
Location: Macclesfield, Cheshire
Posts: 132
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Many thanks, these will be very useful.
Unfortunately a Hard/Reset has not had any effect, both the amplifier and TMC are still showing as ECU not present. I am going to check the voltage supplies to them as all fuses are intact. Hopefully I can resolve the problem as quickly as it occurred. Mike
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| 8th Oct 2019 10:04 pm |
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MELISCAT
Member Since: 17 Dec 2009
Location: Macclesfield, Cheshire
Posts: 132
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Just checked the power to the HK audio Amp, 12v present, checked the optical lead, can only see 1 red light, no light coming from the amplifier - I assume this means there is an issue with the amp? Took the amp out and fitted an optical jumper to the plug.
Stripped the back of the car to access the TMC unit. Checked the optical plug at the TMC end shows 1 red light. No light output from the TMC - is this unit passive? I can't find a power feed to it.
Just ordered some more optical ring jump cables to asses the rest of the network. Is there a MOST connector under the transmission tunnel centre console?
Any additional help or pointers would be of great help Mike
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| 9th Oct 2019 3:10 pm |
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M3bobby
Member Since: 21 May 2018
Location: Sleaford, LINCS.
Posts: 857
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You may be misunderstanding the MOST. The light is fed from the controller (the screen) to each unit in the ring, if you take the MOST off a unit you have broken the ring and the light can’t pass to the unit. To test I remove the most at either end and shine light down one end and you should see it at the other end (obviously you don’t want to use the FO light as you’ll end up blind). 012MY RRS 5.0 Supercharged Autobiography (Current)
Mods:
TPMS (Complete but got an issue)
Genuine LR DRLs (Complete)
Remote Boot close from key fob (Complete)
2016 Discovery 4 Mirrors AKA RRS2 (Complete)
2014 L405 Surround Camera retro fit (Now 2016 L319)
2013 RRS Dual View Screen fit (Complete)
2016 LR4 RSE (Complete)
2014 LR4 Homelink (Complete)
2016 FFRR Electrochromatic Wing Mirror Glass (Complete)
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| 9th Oct 2019 3:51 pm |
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Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10361
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yes, but the controller is the head unit.
yes you only get light out of one end.
The other end receives the light.
Light will not pass thru a unit. The unit has to have power and be working, for it to receive the signals and re transmit them.
The TCM has power supplyed by 1 red wire! Check it has power. (fuse behind glovebox)
no optical connector under console.
as said, you can just use a regular torch. (or even point the end to daylight in the summer) and see white at the other end
unless someone has been working on the car, it's more likely a unit is dead than optics broken, but it all helps with the understanding
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| 9th Oct 2019 6:07 pm |
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MELISCAT
Member Since: 17 Dec 2009
Location: Macclesfield, Cheshire
Posts: 132
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Thanks for the info on the TCM power source, other manufacturers piggy back the power feed to the TCM from the FM aerial amp, via the coax.
Will check the feed tonight to see if there is power. I did realise this afternoon that the unit was likely to only pass a signal if powered up, I have been using a laser pointer that my cats play with, works great. Mike
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| 9th Oct 2019 6:41 pm |
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MELISCAT
Member Since: 17 Dec 2009
Location: Macclesfield, Cheshire
Posts: 132
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Got it. Mike
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| 9th Oct 2019 9:23 pm |
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MELISCAT
Member Since: 17 Dec 2009
Location: Macclesfield, Cheshire
Posts: 132
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Hi, just checked the voltage on the RED wire feeding the TCM it is measuring only 1.1 volts.
It looks like it is being feed from behind the roof lining, is that correct?
I also checked the fuse for that part of the circuit, it was intact and there was 12v at the fuse box. Mike
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| 10th Oct 2019 6:14 pm |
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Pete K
Member Since: 15 Jan 2016
Location: GL
Posts: 10361
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That will be. It then.
See if you can locate the wire on the left side of the boot.
If it’s 12v there either run a new wire over or try and locate the problem.
It’s probably Been crushed somewhere. Typical of landrover build of this era
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| 10th Oct 2019 8:00 pm |
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MELISCAT
Member Since: 17 Dec 2009
Location: Macclesfield, Cheshire
Posts: 132
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thanks, will now have to wait till the weather improves as i don't have a garage. i assume from what you are saying that the cable crosses the head lining and comes out on the passengers side in the boot area? Mike
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| 10th Oct 2019 8:16 pm |
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