BCM Question for footwell lights - Pontiac Solstice Forum
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post #1 of 14 (permalink) Old 07-25-2019, 07:25 PM Thread Starter
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Hey everyone,
(TL/DR at bottom)So, I'm well aware that there has been many posts about adding lighting to the foot footwells. I recently bought the type S kit from AutoZone which I've used in the past and really liked. I want to wire them up to fade with the map light. I read in one of the posts that I can tap into the BCM. My question is, if I unbolt and remove the BCM will that cause any harm to the car or it's computer? Will it need to be reprogrammed? My biggest concern is that if I remove it I screw something up. That being said is it safe to remove the BCM?

In one of the posts I read the user JohnWR said that the wire for the map light is located in A10. I believe the car in that post was a 2006 and mine is a 2009. Is there anything different between the years when it comes to the BCM?

I also read that most people had issues with they're LEDs turning on after 10 minutes or so can anyone give me some advice to avoid this?

As always, thank you for taking the time to read this and I greatly appreciate any and all help.


TL/DR: is it safe to remove the BCM? I would like to tap into the map light wire so my LEDs in the footwell will fade. Is the wire I will use Gray? Thanks again!

Last edited by Gerstech; 07-25-2019 at 07:30 PM.
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post #2 of 14 (permalink) Old 07-26-2019, 01:27 AM
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Why do you want to remove the BCM? The wire you need is in a connector on its face, so there is normally no reason to remove it. That said, there is no inherent danger in removing it, assuming you don't damage it in the process.

The wire you need, A10 in connector X3, was the same in 2008, so should also be the same in 2009. Yes, it is grey.

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post #3 of 14 (permalink) Old 07-26-2019, 05:52 AM
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Quote:
Originally Posted by Gerstech View Post
I also read that most people had issues with they're LEDs turning on after 10 minutes or so can anyone give me some advice to avoid this?
I think you have the wrong end of the stick here

The issue is that the 'fading ground' supplied on the BCM circuit never fully turns the lights off. It reduces the current enough for the factory incandescent map light bulbs not to glow, so in an unmodified car you wouldn't see it. But when you replace those lights with LEDs (or add LEDs to the circuit as you will) they are so much more efficient that you may see a little glow - even though they are supposed to be 'off'.

That glow - if you see it - will continue for a further 10-15mins after you turn off and leave your car, until the battery anti-drain circuitry turns off the supply.

This is normal operation and nothing to worry about, but folks see it and panic that their battery will drain overnight. It won't.

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post #4 of 14 (permalink) Old 07-26-2019, 09:54 AM
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Quote:
Originally Posted by TomatoSoup View Post
I think you have the wrong end of the stick here

The issue is that the 'fading ground' supplied on the BCM circuit never fully turns the lights off. It reduces the current enough for the factory incandescent map light bulbs not to glow, so in an unmodified car you wouldn't see it. But when you replace those lights with LEDs (or add LEDs to the circuit as you will) they are so much more efficient that you may see a little glow - even though they are supposed to be 'off'.

That glow - if you see it - will continue for a further 10-15mins after you turn off and leave your car, until the battery anti-drain circuitry turns off the supply.

This is normal operation and nothing to worry about, but folks see it and panic that their battery will drain overnight. It won't.
This may be a silly question. If you put a resistor across the footwell LED circuit, much like resistors across LED taillights, would this make the LED dim faster?
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post #5 of 14 (permalink) Old 07-26-2019, 10:09 AM
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Originally Posted by joybill44 View Post
This may be a silly question. If you put a resistor across the footwell LED circuit, much like resistors across LED taillights, would this make the LED dim faster?
It would make the LED dimmer at all points (full on or full 'off'). The rate of dimming would not actually increase.
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post #6 of 14 (permalink) Old 07-26-2019, 12:05 PM
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Quote:
Originally Posted by joybill44 View Post
This may be a silly question. If you put a resistor across the footwell LED circuit, much like resistors across LED taillights, would this make the LED dim faster?
The resistor across LED turn signals is there to increase the current draw enough to emulate an incandescent bulb and avoid the hyper-flash caused when the BCM (or flasher) thinks the low-current LED is non-functional. In this case, the resistor may keep the LEDs from glowing by diverting some of the leakage current, but as TS said, it would not change the rate of dimming since that is controlled by the PWM program in the BCM.
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It would make the LED dimmer at all points (full on or full 'off'). The rate of dimming would not actually increase.
I think you are thinking about a resistor in series with the LEDs, which would make them dimmer at all levels. A resistor in parallel with (ie: across) the LEDs would not have an effect on brightness unless it was such a low resistance that its current draw exceeded the capacity of the control circuit and actually caused a voltage drop.

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post #7 of 14 (permalink) Old 07-26-2019, 01:24 PM
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Quote:
Originally Posted by JohnWR View Post
I think you are thinking about a resistor in series with the LEDs, which would make them dimmer at all levels.
Yep. That's how I read it

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post #8 of 14 (permalink) Old 07-27-2019, 08:55 AM
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Interesting. I've been wondering how to wire footwell lights in and I just got my answer.
I'll probably save this mod for the cool weather down time.
Thanks

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post #9 of 14 (permalink) Old 07-27-2019, 07:55 PM Thread Starter
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Hey thank you for the answer the reason I wanted to remove the BCM was to find which wire to use. There are three gray wires coming out of the BCM and I'm worried about tapping into the wrong one and screwing something up. That being said if I don't need to remove the BCM how do I know which gray wire is for the map light?
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post #10 of 14 (permalink) Old 07-27-2019, 08:11 PM Thread Starter
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Quote:
Originally Posted by JohnWR View Post
Why do you want to remove the BCM? The wire you need is in a connector on its face, so there is normally no reason to remove it. That said, there is no inherent danger in removing it, assuming you don't damage it in the process.

The wire you need, A10 in connector X3, was the same in 2008, so should also be the same in 2009. Yes, it is grey.

Hey thank you for the answer the reason I wanted to remove the BCM was to find which wire to use. There are three gray wires coming out of the BCM and I'm worried about tapping into the wrong one and screwing something up. That being said if I don't need to remove the BCM how do I know which gray wire is for the map light?
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post #11 of 14 (permalink) Old 07-27-2019, 10:12 PM
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Connector X3 is the largest of the three on the face of the BCM, and it looks like there are four grey wires in it.
A4 = Door Lock Actuator Control
A5 = Door Lock Actuator Control
A10 = Courtesy Lamp Control
B12 = Instrument Panel Supply Voltage
The rows are A thru D and the columns are 1 thru 12, so you should be able to see which wire you need.

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post #12 of 14 (permalink) Old 07-28-2019, 12:01 AM
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I did the footwell lighting by following threads found on this site. I have a 2007 Sol and had no problems with my leds dimming and going out. yes I took the cover off the BCM found and traced the gray wire ground and taped into it no problems doing it.
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post #13 of 14 (permalink) Old 07-28-2019, 02:30 PM
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I put one multi-color LED light in each foot well. It sticks on the underside of the dash via two-sided tape. It runs on 3 AAA batteries and has a remote control that lets me choose between about a dozen colors. Cost = $5 per footwell light plus 3 AAA batteries. Time invested: under five minutes.

Really basic, I know, but simple, easy and inexpensive.
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Last edited by Knight; 07-28-2019 at 02:38 PM.
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post #14 of 14 (permalink) Old 07-28-2019, 05:16 PM
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I posted pics of where on the BCM you can tie into over on KP and the exact gray wire that is used. Can't post pics here.

How To: install footwell lighting

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