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low beams

7K views 4 replies 2 participants last post by  surly 
#1 ·
I have a 2012 impala, my low beams stopped working. I checked fuses, lamps and replaced switch. They are still out. I cant find a wiring diagram. I know there is a body control module, not sure where it is? Does anyone know where to find a diagram? Im wondering if there is a relay?
 
#2 ·
I would say you may want to do some testing of your wiring on your car.. YEs your car has Relay for both Low and High beams. However they are PCB Relays and I think they are part of your FUSE Box. (NOT changealbe) if the relay is bad it would need new fuse box under hood... I could be wrong but I think that was one of the ones built into the box...

If it was my car, I would go to the BCM Connector 5 Pin 23 (Pink/White) and check for ground when you turn on your headlights. (No ground? Turn head light switch off and on that same wire you tested for ground give it a ground and check headlights) Did they come on?

I wonder if only issue is with Headlights? Also is this an X police car? if it is could be little different on testing as to why I asked...

The fuses also for the head lights are in the engine bay. There will be a 10 amp for left low and right low beams also 10 for high left and right. The Relays are one for High and one for LOW but again I think they are PCB and built into the fuse box... Could you take a picture of your underhood fuse box

James
 
#3 ·
Sorry that was only half the answer. Also for the Low beams after the Fuse, Leave box goes into a Yellow wire for the left Low, Then from that yellow wires goes into a wiring connector and color of wire changes to Green. For the right low, leaves the fuse box in a Tan/White wire, Where it makes a connection and changes to green as well...

High beams for left and right are blue wires for 12v at the bulbs. That way you know lows are Green and highs are Blue at the blub.
 
#4 ·
So I went and looked over my 06, Same wiring from the BCM and Relay/Fuse box. Sorry forgot to ask. When you have your car off and all lights off, Then you go to start your car and your Day time Running lights come on! Does your Headlight work then?

There are 4 fuses related to the head lights. 3 realys. All PCB and not changeable in my model year may have changed into yours but doubt it.

Body control grounds out a purple wire, this turns on the DRL relay at underhood fuse box that passes DRL fuse 1 and back DRL fuse 2 Splits off to left and right low beam fuse, then to the low beams. THen ground for Low beams to complete the circuit.

IF light is turned on via switch, BCM grounds out Pink White wire that goes to the underhood fuse box turns on Low beam PCB Relay and then follows same path that the DRL were going to start with... Only difference from my 06 to your car is just before the light it don't change to green it stays yellow and tan/white to the bulb...

It could be that your test for the BCM Pink/white Ground works when you turn on the lights, Fuses are ok. Testing pas the fuses out to the lights at the green wires or even before that connector yellow and tan/white you have power. Bulbs good, THen make sure your grounds are good. There is a Splice for the grounds, One to the highs and one to the lows from the splice to Body ground. So could be fault at power from relay (HOpe not) or ground. Worse case BCM. However I would also look over your Grounds at your BCM. Your BCM is mounted under drivers side dash.

James
 
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