Morning all,
Seeking some wisdom from the collective.
I’ve a 2009 ( but 2010my) l322 3.6tdv8.
In my ownership I’ve never been able to communicate with the FBH using my diagnostic equipment ( Britpart Lynx ). However the FBH is obviously still communicating with the vehicle as it had logged a glow plug fault in the hevac module which when cleared and having reset the FBH ( removal of fuse for 30 secs ) allows the FBH to operate via the head unit, but still no coms via diagnostics with FBH. Also it won’t actually heat when using the remote, ie it starts the sequence of ignition but packs up leaving the cabin blowers operating.
More recently I’ve noticed I’ve lost coms with the immobiliser module via diagnostics. Everything still works as it should.
Diagnostics also reports no coms with the passenger seat module, and the lighting control module. But as I’ve said everything, seats lights etc still operate as they should.
I’ve performed a resistance test on the high speed and medium speed busses and they’re both at 60ohms which would indicate the the terminal resistors are ok and I assume that both legs of the buses are still intact.
My suspicion is that the medium speed bus has a low voltage fault , probably through a bad contact.
Could anyone tell me the following.
What voltage am I looking for on both legs of the high speed bus? and the medium speed bus ?
Also voltage for the Lin bus and K bus might be useful.
Is there actually a passenger seat module in the 2010my variant or is it part of the drivers seat module? ( I’m aware that Britpart Lynx shows modules as no coms, if they don’t exist)
My Britpart Lynx diagnostics is the original wired version which does list the 2010my as an option. Has anyone had difficulty using this on a 2010my ? and might there me a better and more comprehensive option ?

Is this maybe being over-thought?

The FBH won't fire and only vents will activate for "cabin ventilation" when the ambient temperature is above 5 degrees. So, unless you can fool the resistance of the ambient air temperature or create an artificial environment around it, you won't get hot air produced.

Otherwise, have you considered a firmware version issue or fault with your diagnostics opposed to an issue with the actual car? From what you've written, you state everything else is working on the vehicle, so you may be chasing a fault which doesn't exist, especially as L322s are well known for their spurious and plentiful ECU faults. 2015 Range Rover Autobiography 4.4 SDV8

Hi Garry,
Thanks for your reply.
The fault with the FBH, I’ve been chasing down for well over a year and definitely whilst it’s been cold enough to operate.
Perhaps I wasn’t clear enough it will operate and heat when initiated through the head unit. However it does everything but heat when operated through the remote. But I still can’t communicate with it.
However more recently and I could before, I can’t communicate with the immobiliser module, and I need to initialise another key.
The reason I ask about the seat module is I can’t communicate with it either and from what information I have the seat module also communicates on the medium speed bus. However when I’ve looked I can’t actually see a physical module in the passenger side seat. Hence why I asked if anyone knows wether e seatodule is part of the drivers side seat module.
Yes I’ve considered whether my diagnostics might be up to the task on the later models, that why I’ve asked if any one else has had similar problems.
To conclude I’m fairly certain Ive got a voltage issue on the medium speed bus and I suspect it’s either through a corroded connector or splice or earth point. Which is why I asked if anyone specifically could tell me the voltages to look for in this model year of vehicle.
But before I go pulling the dash apart randomly, it’s a lot easier and logical to test the bus with a meter.
Diditg

Have you checked the fuel pump for the FBH is functioning correctly?

If it has failed, the FBH also won't activate in cold weather. 2015 Range Rover Autobiography 4.4 SDV8

Hi again Garry,
The fbh fuel pump is good
The fuel burning heater does activate in cold weather through the head unit. It doesn’t when using the remote.
To be fair, I can live with the fuel burning heater the way that it is, it’s the lack of communication with the immobiliser which is causing me concern.

Have you followed the re-learn procedure for the remote and also replaced the battery? The remote needs a very specific 3.0V to operate.

I tried one battery and it didn't work at all. Replaced it with a Duracell and all started working. 2015 Range Rover Autobiography 4.4 SDV8

As Gary says if everything is working, apart from a minor FBH issue, then it's pointing towards your reader... most on here use the Gap IID tool, or take it to an Indie and get them to see if they can talk to all the ECU's....  Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

garyRR wrote:

Have you followed the re-learn procedure for the remote and also replaced the battery? The remote needs a very specific 3.0V to operate.

I tried one battery and it didn't work at all. Replaced it with a Duracell and all started working.

Haylands wrote:

As Gary says if everything is working, apart from a minor FBH issue, then it's pointing towards your reader... most on here use the Gap IID tool, or take it to an Indie and get them to see if they can talk to all the ECU's....

Just so there's not confusion, I mean the battery in the FBH remote, not the car battery.

The other thing you can do if your FBH by remote isn't working is disconnect the telestart multiplug in the boot and link the +ve and switched live connectors to make sure the fault isn't with the Telestart unit or remote. Again, has to be done when the ambient temperature sensor is below the threshold temperature. 2015 Range Rover Autobiography 4.4 SDV8

Temperature at which FBH provides heat to the cabin will be in your handbook
It varies by model / model year
For L322 MY10-12 it is 15 degreees C. (That’s what it is for my MY11)