Lighting control module

MATT1458

MEMBER
2004 MERCURY MARQUIS
4.6L
V8
2WD
AUTOMATIC
96,000 MILES

I replaced the LCM, the lights kept cutting off. But before that I bought a Doorman Bypass and used it for day. I do not recommend it. But, I had problem with it. It kept my lights on all positions even on the off. Well I figured that I should just dive in and buy a new LCM. So I did. It's been a week and now I'm having same problem. Maybe it could be I'm switching the lights to quick to off? I don't know but the headlights will remain on. I can shut the car off and sometimes the lights will kick off. But, I am leaning towards the light switch (on/off) itself is getting bad.

Saturday, February 27th, 2021 AT 3:23 AM

3 Replies

KASEKENNY

MECHANIC
18,907 POSTS

This could be but do you have the switch in the Auto position? If so, we need to test the voltage coming out of the switch to the LCM on this circuits highlighted.

https://www.2carpros.com/articles/how-to-check-wiring

Basically we need to see if the switch is telling the LCM to keep the lights on or not. What I suspect is happening is what you are thinking that the switch is the issue. The reason is, when you have it set to off, the LCM should have a delay programmed into it. However, if the switch is shorted then it will tell the LCM to keep them on.

I attached the wiring diagrams below for your review. Let me know what questions you have and we can go from there. Thanks

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Sunday, February 28th, 2021 AT 1:45 PM

MATT1458

MEMBER
2 POSTS

Thanks for the reply, but the the lights will remain on. In the off position. I never run the auto lights. I will have the lights on or I will have them off. I do use the parking lights position a lot as well. But I will look into the light switch and test it. Thank you.

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Tuesday, March 2nd, 2021 AT 9:41 AM

KASEKENNY