P38A Interior lights staying on

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SpanishTony

SpanishTony

Active Member
Posts
297
Location
Cheshire
Noticed when I was driving this morning that all the interior lights were on and haven't gone off when I got out of the car and locked it.

Any suggestions?
 
Do you mean pressing and holding the light button until the message comes up in display panel? If so I've tried that without any luck. Have removed the bulbs as a temporary solution. Do you know if I also have to remove the one in the tailgate?
 
Not sure about the tailgate bulb. I would think that only comes on with the tailgate open but not certain.
From memory, the door switches are part of the latch mechanism so if it's not working properly then I guess it's time to delve into the doors.
Are you getting any door open messages on the dash?
Try opening and firmly closing every door.
I would think that if you have no "door open" messages, the lights should work as expected.
I'm guessing that the lights circuit is fed from the BECM so if the BECM is getting the correct signal but lights are staying on then there must be an issue with the BECM.
Do you have nanocom?
 
OK, I don't have mine to hand as I'm working away in Spain at the moment.
However, I would guess that if all doors give an open message and they all go away with all doors shut, then the BECM will be getting the correct information.
I can't remember the exact way they operate but I think you have 3 options.
1. Lights on all the time.
2. Lights on when door open.
3. Lights off all the time.
Now, the press and hold I think switches between lights on with doors and lights off but I can't remember how they switch on permanently. I think it's a quick press on the button or a separate switch.
If you press and hold the button, do you get the message in the dash? If not, it could just be that the button is dicky and has been left in the permanently on setting.
 
Right, just looked in the owners handbook.
If you press and hold the centre switch above the mirror, you should get a beep and "int lights on" or "int lights off" in the display.
If int lights on is set, they should come on with the doors and go out 10secs after closing the door or as soon as you start the engine.
In this mode you should be able to switch them on and off manually with a short press on the centre button. If they are left on in this mode, they should time out after 10 minutes anyway. (apart from the map lights, if they are on, they stay on until the battery is dead)
I would try and see if they time out after 10 minutes then at least you know the BECM can control them.
I asked about nanocom because you might be able to control them with that to prove BECM is OK.
 
The individual buttons are only for the map lights, not the main interior lights.
The main interior lights are controlled by the centre button above the mirror (and the doors if selected)
 
OK, so map lights are working OK then.
So, if you press and hold the centre button above the mirror, what happens?
 
Nothing, unless I hold it long enough to get the lights on message in dash display and if I press and hold again I get lights off message
 
SpanishTony said:
Nothing, unless I hold it long enough to get the lights on message in dash display and if I press and hold again I get lights off message
Click to expand...
OK, that tells me that the button is working OK.
So, it appears that there is either a wiring fault after the BECM or the BECM itself is at fault.
I don't have access to the wiring at the moment. If the lights are negative switched, a short to earth from BECM to the lights would keep them on all the time.
Needs some digging by the sound of it.
 
Grrrrrr said:
The door ajar signal comes from the lock actuator iirc. That would trick the BECM into putting the lights on all the time. Or an earth fault. @martyuk would know for sure but think he might be working away.
Click to expand...
But then there would be a door ajar message on the dash.
My guess is a short to earth between the BECM and the lights
 
Yes, door ajar switches are in the latches - and should trigger a door open warning.

To test fully you'd need to probe the wiring to trace where it's coming from. It could also be worth checking/removing/disconnecting the rear interior lights, as the switches on these are for manual/auto operation - a dodgy switch or something in there could cause a permanent ground connection too - but unplugging the rear lights would eliminate that.

If you have a Nanocom, then it is possible to both check the status of the door inputs, to make sure they are behaving as they should - it's also possible (from memory) to drive the interior light output aswell.

Do the lights go out when the vehicle is locked/alarmed? or just permanently on, no matter what?
 
ok, so has to either be a short in the wiring, which keeps them grounded all the time, or maybe the transistor in the BECM has failed in a grounded state, so it's providing a constant ground source.

I would unplug the rear lights, and the tailgate/loadspace lamp (I found the connections on my loadspace lamp were getting corroded and one broke off in the end - which if that touches metal could cause the problem too) one by one to see if it makes a difference - working through to them all being unplugged. If you still get the footwell lamps on for example, then it could be the component in the BECM.

The good news is that they are replaceable, and I'd be happy to have a look at it for you... The bad news... I'm not home for long enough until January to do anything with it.
 
Thanks Marty, not sure I have footwell lamps. Have taken all the bulbs out for the moment but will try your suggestion tomorrow and report back.
 
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