Hi all very impressive knowledge reading through the threads on this forum I don’t suppose any has ever experienced this sort of fault. Drive along and all of a sudden goes into limp mode and all the dash lights come on every single one the information screen displays every fault you can think off. Every system unavailable. Stop switch it off and re start the engine management light stays on and says eco mode unavailable. The car runs fine. Eventually the engine management light goes off. Then a few more miles down the road it happens again.
Maybe your battery and alternator are not as they should be?
What Battery volts do you have with everything off, with just ignition on, when cranking?
What battery volts do you have when the car is revving at c.2,000rpm with everything switched on (lights/A/C/Heated seats/screens etc.)?
What Battery volts do you have with everything off, with just ignition on, when cranking?
What battery volts do you have when the car is revving at c.2,000rpm with everything switched on (lights/A/C/Heated seats/screens etc.)?
Okay may not be good enough, the larger land rovers love a good battery.
The cheapest of the cheap multimeters off ebay etc will do you for testing battery and alt voltages.
They just put a tester on the battery it was reading 16 volts which I thought was too high. But the chap said it was fine. All the connections are tight. They didn’t test the start stop battery. I only took it there as was only place open. I’m trying to get it booked into a Land Rover specialist This week.
16 volts is to high.
D3 max volts is approx 15.1/2 in the depths of winter, I ahve a volt gaige on the dash and it is the same year after year.
D4 normal batteries much the same voltages.
D4 with AGM batteries runs at a lower voltage.
So I would conclude your alternator is duff, which in turn may have screwed the battery.
I bet @gstuart will know the D4 volts, but he will need to know the year of your car
Hi
Plus 1 what’s already been mentioned , indeed 16 Vdc is too high for a D4 , max for the AGM batteries is 14.8 Volts., D3 is 16.5 Vdc
here’s also a picture ref that earth lead thats behind the front OS wheel arch liner
plus 1 in getting a multimeter , see what the battery is with the engine off and then engine running , followed by putting everything on, Ie lights , AC etc , then raise it to 2,000 revs and see what the Vdc is , then with the engine still running at idle , meter set to ACV , put the test probes across both battery terminals and read the voltage ,
For testing grounds , go from the positive battery post to a ground u wish to test
lhas the BMS module been reset and put onto diagnostics as that’s also a very useful knowing if there’s any codes
at the end of the day if it is at 16 Vdc that will as indeed mentioned screw ur AGM battery up so will req replacement but only after the alternator is fully checked out , if the alternator needs replacing it must be a Denso
would u be so kind to let us know what year the D4 is and if it’s a stop start plse , thks
hope that also helps u
ps, battery should be a minimum of 825 amps - 90 A/H
Plus 1 what’s already been mentioned , indeed 16 Vdc is too high for a D4 , max for the AGM batteries is 14.8 Volts., D3 is 16.5 Vdc
here’s also a picture ref that earth lead thats behind the front OS wheel arch liner
plus 1 in getting a multimeter , see what the battery is with the engine off and then engine running , followed by putting everything on, Ie lights , AC etc , then raise it to 2,000 revs and see what the Vdc is , then with the engine still running at idle , meter set to ACV , put the test probes across both battery terminals and read the voltage ,
For testing grounds , go from the positive battery post to a ground u wish to test
lhas the BMS module been reset and put onto diagnostics as that’s also a very useful knowing if there’s any codes
at the end of the day if it is at 16 Vdc that will as indeed mentioned screw ur AGM battery up so will req replacement but only after the alternator is fully checked out , if the alternator needs replacing it must be a Denso
would u be so kind to let us know what year the D4 is and if it’s a stop start plse , thks
hope that also helps u
ps, battery should be a minimum of 825 amps - 90 A/H
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I’ve just checked it again with my multimeter on the main battery I have 12.42 v with engine off when charging I have 14.8. The smaller battery the other side of the engine bay o have 13.36 when engine off 14.43 when charging
When reving at 2000 rpm main battery was stayed at 14.8 then dropped to 14.03 and back and forth
The small battery stayed the same at 13.36
The discovery is a 2014 on a 14 plate and it does have stop start many thanks Adam
When reving at 2000 rpm main battery was stayed at 14.8 then dropped to 14.03 and back and forth
The small battery stayed the same at 13.36
The discovery is a 2014 on a 14 plate and it does have stop start many thanks Adam
biketeacherdave
Well-Known Member
You have a smart charging system on the D4 as the battery gets weak the car demands more power from the alternator hence getting 16volts when running and when checked by halfrauds .
Replace the battery but you then need to tell the car it has a new battery or it will keep pumping 16volts into it and cook it pretty damp quick.
Replace the battery but you then need to tell the car it has a new battery or it will keep pumping 16volts into it and cook it pretty damp quick.
Hi all do the disco has been in the garage since Tuesday. Brilliant group of guys. They know it’s loosing its high speed can-bus. But they’re having a hard time finding what the cause is. Typically the car has behaved itself on the four test drives they have done. But they’re leaning towards either the battery because the one on there is not a good quality make or the battery monitoring system. There is a relatively new alternator on it which tell me that this problem has been on the car for a while. Why did I have to buy one with electrical gremlins lol 
Hi
first i would see what make the alternator is plse as if it’s not a Denso it will req replacement , there extremely fussy
if it’s got a high speed canbus error they should be able to trace which module is causing the issue, including live data logging along with the 5 Vdc reference voltage supply and testing earths with multimeters or a graphing meter
indeed a bad battery or alternator will cause havoc on the system
been there done that when I had a serious canbus issue which I managed to track down by going through the system step by step
first i would see what make the alternator is plse as if it’s not a Denso it will req replacement , there extremely fussy
if it’s got a high speed canbus error they should be able to trace which module is causing the issue, including live data logging along with the 5 Vdc reference voltage supply and testing earths with multimeters or a graphing meter
indeed a bad battery or alternator will cause havoc on the system
been there done that when I had a serious canbus issue which I managed to track down by going through the system step by step
If it's a stop start car, it needs an agm battery. When either the main battery or second battery are replaced the car needs to be told via diagnostics to reset the charge rates or it'll cause premature battery failure. Also check the charge device near the second battery for loose or burnt terminals. The plastic coverd nuts that hold the cables tight could be burnt. Replace them for traditional nuts as a safe guard. They heat up and lose grip of the cables resulting in shorts through the wires. 
