Headlights problem

[bobbyjoes]

Ok,I have a 2011 impala lt I just got,j drive a company pickup so car don't get used much;few days ago was going to go somewhere at night ;Well I had brights and everything else but no lows;checked fuses put new bulbs in ,now during the day I have lows or daytime lights but no brights and as soon as it's gets dark I have brights that's it,during the day the bright symbol wouldn't come on for brights but does come on for flash and pass and at night they both work,I have no idea, hope this all makes since,could use some help,thanks

[Stealthee]

I know some of the earlier cars had problems with the HDM module, which is essentially the low beam relay. That is where I would start.

[Tech II]

The headlamps are controlled by 3 relays, which are all controlled by the BCM.....

OK, you are saying if you manually turn on the lights, you only have high beams(indicator on), and when you switch to low beams, no headlights at all(high beam indicator goes out)?

[bobbyjoes]

Ok ,at night with light switch to auto or manual all I have is brights with indicator on no lows,then during the day at random. I will have lows but no brights and the indicator won't ligh t up either,I will check today again,do est make since

[Tech II]

Ok, let's do a step by step check here.....

With headlights in auto position, start car.....go outside and check the lights.....your low beams should be on at half brightness of normal.....your tail lights should be off....this is DRL mode....

Now switch to manual headlights......your low beams should be on at twice the brightness of DRL's mode.....if the high beam indicator is on in the cluster, push the directional lever, AWAY from you.....the high beam indicator should be off and the low beams should be on at twice the brightness of the DRL mode......and your tail lights should be on in either high or low beams....to get hi beams back on, pull the lever TOWARDS you, and the hi beam indicator should now come on....

Do all these steps check out?

[bobbyjoes]

Originally Posted by Tech II

Ok, let's do a step by step check here.....

With headlights in auto position, start car.....go outside and check the lights.....your low beams should be on at half brightness of normal.....your tail lights should be off....this is DRL mode....

Now switch to manual headlights......your low beams should be on at twice the brightness of DRL's mode.....if the high beam indicator is on in the cluster, push the directional lever, AWAY from you.....the high beam indicator should be off and the low beams should be on at twice the brightness of the DRL mode......and your tail lights should be on in either high or low beams....to get hi beams back on, pull the lever TOWARDS you, and the hi beam indicator should now come on....

Do all these steps check out?

ok,im coming from a 98 buick so excuse me if im not sounding to smart,ok went there this morning on auto the DRL are on with no marking lights,when i turn to manual no lows but markings are on,put brights on they work with markings ,so no low beams is the the problem,i have checked the fues and bulbs,hope this makes more since,ha

[Tech II]

You have 3 headlight relays...swap the low beam relay with the high beam relay, and see if the lows now come on....

If they still don't you will have to attach a wire to the control leg of the low beam relay, and then ground the other end of the wire....if the lights now come on, the BCM is not grounding the relay.....

Either a bad BCM, or bad input from the multifunction switch to the BCM....

[bobbyjoes]

So what do you think?

[bobbyjoes]

S0rry I didn't see reply ,will check it out,thanks

[bobbyjoes]

Well i gave up and brought to dealer,hope it don't cost to much,I have extended warranty but who know what they cover,will let you know ,thanks

[bobbyjoes]

Ended up being bad fuse block,thanks for the help,appreciate it

[Tech II]

Yes, there have been UBEC problems....more often than not, the bolts that pull the blocks of wires together sometimes become loose, which can cause an arcing problem....