My battery issue!! Starting to do my head in!!

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mattstevenson2005

mattstevenson2005

Active Member
Posts
548
Location
Manchester UK
Hi guys,

Just been trying to sort my battery drain issue out again and I have narrowed it down to the BCU (body control unit) not going to sleep propperley as it's still drawing 0.7mA when the car has been left for over an hour, I have had the body control unit out and have inspected the pins and wiring for corrosion but all seams fine. Any body have any other ideas what could be keeping the BCU awake? :(

Thanks
Matt
 
Yer sorry meant 0.7amps, it's been a long day :(

UPDATE: I think I have made some progress, i don't think is the BCU unit causing the issue any more, After having the passenger seat out of the car and doing some drain tests on the BCU i have traced the problem further to the diagnostic port, with the diagnostic port cover closed (I.e. In the up position with the 3 pins in the cover connected to the port itself) the car draws 0.7amps when asleep, when the diagnostic port cover is open (I.e. In the down position with the 3 pins in the cover not connected to the diagnostic port) the car draws 0.03amps! (30mA) this is with the car locked and alarmed.
My question is will leaving the diagnostic cover open cause any problems when the car is parked, locked and alarmed? As this will temporary solve my battery drain issue until I can find the root cause, will the alarm still work etc... With the cover off the port?

I'm getting there! :)

Thanks
Matt
 
Last edited:
mattstevenson2005 said:
Yer sorry meant 0.7amps, it's been a long day :(

UPDATE: I think I have made some progress, i don't think is the BCU unit causing the issue any more, After having the passenger seat out of the car and doing some drain tests on the BCU i have traced the problem further to the diagnostic port, with the diagnostic port cover closed (I.e. In the up position with the 3 pins in the cover connected to the port itself) the car draws 0.7amps when asleep, when the diagnostic port cover is open (I.e. In the down position with the 3 pins in the cover not connected to the diagnostic port) the car draws 0.03amps! (3mA) this is with the car locked and alarmed.
My question is will leaving the diagnostic cover open cause any problems when the car is parked, locked and alarmed? As this will temporary solve my battery drain issue until I can find the root cause, will the alarm still work etc... With the cover off the port?

I'm getting there! :)

Thanks
Matt
Click to expand...

Oh dear, 0.03amps is 30ma not 3ma. 30ma is, I would guess, about right, it would be for a P38.
For future reference, 1 amp = 1000ma .1amp = 100ma .01amp = 10ma .001amp = 1ma:D
 
Datatek said:
Oh dear, 0.03amps is 30ma not 3ma. 30ma is, I would guess, about right, it would be for a P38.
For future reference, 1 amp = 1000ma .1amp = 100ma .01amp = 10ma .001amp = 1ma:D
Click to expand...

I did it again! :doh: it been a very very long day staring at wiring diagrams and tracing wires :(. Yer meant 30mA :doh:

Matt
 
WORKED IT OUT!! :)

After dismantling and removing my entire dash and instrument cluster this morning i have traced my drain to the headlights!! The previous owner had the 2008 facelift done so the headlights are the new type, and it is these are causing the excessive drain on the battery, if i remove the connector from the back of each headlight the drain falls to 30mA which is what it should be, as soon as i put the connectors back in the rear of the headlights the drain rises to 700mA!! :(

Does anyone have the wiring diagram that is used when fitting these new type headlights to an older L322 e.g. the conversion guide

Thanks in advance
Matt
 
Thats curious, are they normal type headlamp bulbs or HID? If they are normal type bulbs, it's difficult to see why they should affect the BCU unless there is some sort of current leakage to ground. If they are HID there are a number of possibilities but I'm not well enough informed to give you a definative answer. It's also odd that opening the diagnostic port also cures the excessive drain. It could be that opening any circuit will lower the current drain, try removing a rear light connector.
By the way, congratulations on your diagnostic skills.
 
Last edited:
Datatek said:
Thats curious, are they normal type headlamp bulbs or HID? If they are normal type bulbs, it's difficult to see why they should affect the BCU unless there is some sort of current leakage to ground. If they are HID there are a number of possibilities but I'm not well enough informed to give you a definative answer. It's also odd that opening the diagnostic port also cures the excessive drain. It could be that opening any circuit will lower the current drain, try removing a rear light connector.
By the way, congratulations on your diagnostic skills.
Click to expand...

Hi mate, cheers mate! :) i dont think they are affecting the BCU after doing loads of tests on it the BCU appears to be working correctly, just me jumping to the conclusion that the BCU was playing up, but it appears to be working correctly. With regards to the headlights they are the ones fitted to the 2008 range rovers, they have those ultra bright white xenon dip beams, so i presume they are HID lights. Although the full beam is a halogen bulb i believe. Im going to take it to my local garage tomorrow night on the way home and get them to plug the car into their diagnostic system with the headlights disconnected to see if it is them that is causing the no communication problem.

I will give the rear light test a try and report back in a bit.

Thanks
Matt
 
mattstevenson2005 said:
WORKED IT OUT!! :)

After dismantling and removing my entire dash and instrument cluster this morning i have traced my drain to the headlights!! The previous owner had the 2008 facelift done so the headlights are the new type, and it is these are causing the excessive drain on the battery, if i remove the connector from the back of each headlight the drain falls to 30mA which is what it should be, as soon as i put the connectors back in the rear of the headlights the drain rises to 700mA!! :(

Does anyone have the wiring diagram that is used when fitting these new type headlights to an older L322 e.g. the conversion guide

Thanks in advance
Matt
Click to expand...
Hi Matt i hate to sat this but i dont see how the headlights can be the cause, have you tryed disconnecting the plug from the light switch? if so does the amp draw drop then?.
 
Power is getting to the head light from some where when you pull the plug of the light unit all your doing is braking the powers route to earth. Have your head light got electric adjusters on them?
What you need to do is find which of the positive fead wires is causing it. theres a couple of ways of doing this.
 
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oldskool said:
Power is getting to the head light from some where when you pull the plug of the light unit all your doing is braking the powers route to earth. Have your head light got electric adjusters on them?
What you need to do is find which of the positive fead wires is causing it. theres a couple of ways of doing this.
Click to expand...

Hi oldskool, have just tested the connectors and they are both recieving 12 volts on pin 5 (which is purple/white cable)

Matt
 
Last edited:
oldskool said:
Ok do you know what that pin feeds is it the headlight adjusters?
Click to expand...

Have just done some research using the RAVE and my trusty meter and it turns out that the white/purple wire is a direct 12v feed from the diagnostic socket for when using Testbook/T4, on pin 8 of the diagnostic socket, this is why when the diagnostic socket cover is removed the drain stops, need to trace back now why FUSE 15 in the glove box, which supplies the diagnostic socket is not disconnecting when the car is asleep.

Matt
 
mattstevenson2005 said:
Have just done some research using the RAVE and my trusty meter and it turns out that the white/purple wire is a direct 12v feed from the diagnostic socket for when using Testbook/T4, on pin 8 of the diagnostic socket, this is why when the diagnostic socket cover is removed the drain stops, need to trace back now why FUSE 15 in the glove box, which supplies the diagnostic socket is not disconnecting when the car is asleep.

Matt
Click to expand...
Are you sure? sounds more likly that the diag socket is powered by the same fead as something in the head light what does that wire go to in the head light?
 
Dont be confused cos something is staying powered up when car ignition is off, the engine module has a permenent live for a start. So does your stereo
 
i have just checked when i remove the cover from the diagnostic socket the voltage on the pin in question on the headlights drops to 5.5v ???? :confused: and the drain on the battery drops from 700mA to 30mA
 
mattstevenson2005 said:
i have just checked when i remove the cover from the diagnostic socket the voltage on the pin in question on the headlights drops to 5.5v ???? :confused: and the drain on the battery drops from 700mA to 30mA
Click to expand...
Ok I give up. You have found where the powers going, through the headlight, youve found what wire its going through, you now need to find what that wire feeds in the head light.
 
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