P38 Power Drain

O.K I am now getting irritated by leaving my Range Rover on trickle charge and would like it sorted.... does anyone know of a mechanic (or ortherwise) who is the mutts nuts at this sort of thing.... North Wales / Chester area prefered....

Thanks in anticipation.

Its a 2002 P38 if that makes a difference !

If you describe the symptoms and what you've tried already you might get some suggestions at a fix, many people have suffered from this....

That is the sympton... use it daily she fires on sight of the key, leave for a three days (avg) and it you don't even have central locking.... and before the I hate P38's brigade all start singing in harmouny... a lot of modern vehicles suffer from these issues...

Has it always done it, or is this a new thing? Many of the faults people have experienced have been related to EFI causing the cars electronics to remain awake, rather than going into standby as they should. Is there a new transmitter of any kind nearby, cell tower, traffic or other telemetry point etc.?

Its always done it, and I have lived with it, when its goes for service I ask them to have a look whilst its there, but the fixes so far have not cured the problem

Take the blue wire off the RF receiver located under the R/H trim panel in the boot and have the capacity of your battery checked.

I have had four battery's in three years, all premuim grade. The latest is only 4 months old and its a genuine part.

They have fitted an isolator switch to the the gubbins under the rear trim, that has'nt worked, but it does make the vehilce unstealable ! (mind u the flat battery does that too)

MSX150 said:

I have had four battery's in three years, all premuim grade. The latest is only 4 months old and its a genuine part.

They have fitted an isolator switch to the the gubbins under the rear trim, that has'nt worked, but it does make the vehilce unstealable ! (mind u the flat battery does that too)

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Petrol or diesel and what capacity batteries have you fitted?
You need to see if the BECM is actually going to sleep.
Have you tried pressing the mode button? Apparantly this forces the BECM into sleep mode, I haven't tried it though.

the mode button as in on the gearbox? got to be worth a try, i will do it now!

well it switched off the little red light for park gear, so at the very least thats a bit of battery saved.... if it sorts out the problem.. i will be well chuffed to say the least!

Oh well worth a try, pressed on Sat when I got the post, jumped in for work this morning and it just caught, one more turn of the starter and it would have been jump leads..... so I'm still looking for someone good at diagnostics if anyone has a recommendation ?

MSX150 said:

Oh well worth a try, pressed on Sat when I got the post, jumped in for work this morning and it just caught, one more turn of the starter and it would have been jump leads..... so I'm still looking for someone good at diagnostics if anyone has a recommendation ?

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Get the alternator checked for leakage current.

Have you disconnected the RF lead? If not try this first as I suffered from this last year, lots of Wi-Fi in my areas kept the electronics awake. see my profile for pics on how to do this...

As I say, I have had an isolator swithed fitted, as the garage was convinced this was the problem, I now flick a switch and it renders my fob useless, therefore I presume nothing else should wake it? that being said, the park light still glowed dimly, until I pressed the mode button as recommended by datatak..... I will check the alternator for leakage current, although I have ready been told by one "diagnostic engineer" that the drain is quite significant, he just never found the root of the problem....

Although I have disconnected the Blue wire completely, I can still use the Key fob, it may be worth seeing which wires they have isolated. With the blue wire unplugged, I can still open the doors etc , but it just means that you need to be closer to your car for it to work.....

MSX150 said:

As I say, I have had an isolator swithed fitted, as the garage was convinced this was the problem, I now flick a switch and it renders my fob useless, therefore I presume nothing else should wake it? that being said, the park light still glowed dimly, until I pressed the mode button as recommended by datatak..... I will check the alternator for leakage current, although I have ready been told by one "diagnostic engineer" that the drain is quite significant, he just never found the root of the problem....

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Are you completely disconnecting the RF receiver not just aerial? Could be the RF receiver itself is duff. The other thing that will cause battery drain is the engine compartment fuse box. Check for burning smells and look at relays 6 & 7.

MSX150 said:

the mode button as in on the gearbox? got to be worth a try, i will do it now!

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Pretty sure that just turns the little red light off, but the becm stays awake, you can hear a faint electical noise if you listen very carfully.
Have you tried leaving the car unlocked? My becm stays awake if you lock it but sleeps if you dont!!

o.k got a few things to try..

I have checked my service bills, Ive had the BECM replaced... that did'nt do the trick... next service they replaced the RF recevier...
Datetex, if the alternator is showing a significant leakage would this mean the alternator is duff ?

I found this useful in trying to figure out my battery drain problem.
BECM Sleep Test
This test will determine if the BECM goes to sleep properly or it will stay awake.

1. Sit in the vehicle in the driver seat with all the doors closed.
2. Wait until the interior light switches off.
3. Switch on the ignition.
4. Switch off the ignition.
5. Open the driver door and leave the door open for the reminder of the test.
6. Switch off the interior lights by pressing the button for 4 seconds. On the message centre you can observer the message "Lights off".
7. The message centre displays "Ignition key in" for approximately 2 minutes.
8. If the display goes blank after the two minutes, then the BECM is gone to sleep, if the display is still on, then the BECM did not go to sleep.

i found my becm was sleeping correctly but continued to watch the message display and red gearbox light and found that something was waking it up again very shrtly after it was sleeping. traced it to a wireless weather station the missus had moved into the front room .