Headlights not wokring?

Tiny
JOSH08GRANDPRIX
  • MEMBER
  • 2008 PONTIAC GRAND PRIX
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 60 MILES
Hello, I have a 2008 pontiac grand prix my driver side low beam is not working. I checked the fuses and the bulb and they are both ok. What else could it be?
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Tuesday, February 15th, 2011 AT 12:34 AM

35 Replies

Tiny
JDL
  • EXPERT
Use a voltage tester on the fuse circuit, headlamps on. If no voltage, backtrack the circuit. In the diagram, the yellow wire at headlamp is voltage. Black wire is ground.
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Tuesday, February 15th, 2011 AT 7:15 PM
Tiny
JDL
  • EXPERT
Just to add, you may need to check for trouble codes? I have seen the alternator put out to much voltage popping the headlights.
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Tuesday, February 15th, 2011 AT 7:21 PM
Tiny
JESSE787
  • MEMBER
  • 2008 PONTIAC GRAND PRIX
  • 94,000 MILES
Both of my head lights went out yesterday for some reason. All the other lights work its just both of my headlights
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Wednesday, December 9th, 2020 AT 8:37 AM (Merged)
Tiny
RASMATAZ
  • EXPERT
Could be the headlight switch or a relay to include the fuse/s that powers it-
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Wednesday, December 9th, 2020 AT 8:37 AM (Merged)
Tiny
MILKMAN96
  • MEMBER
If it's not the switch or relay
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Wednesday, December 9th, 2020 AT 8:37 AM (Merged)
Tiny
KHLOW2008
  • EXPERT
It could also be due to bad wire connections or a fault with the Body Control Module.

Get a scan done to check if there are any trouble codes.
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-2
Wednesday, December 9th, 2020 AT 8:37 AM (Merged)
Tiny
DONALDPIERCE73
  • MEMBER
  • 2007 PONTIAC GRAND PRIX
  • V6
  • 2WD
  • AUTOMATIC
  • 185,000 MILES
Replaced switch because it was bad. Everything worked other than high beams kicked on wouldn't shut off unless you held the switch. Put new switch on blue light turns on and off like it should but lights won't kick on into high beams. I've checked fuses and relays and things just can't figure it out. Any solution?
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Wednesday, December 9th, 2020 AT 8:39 AM (Merged)
Tiny
STEVE W.
  • EXPERT
Hate to say it but the switch likely wasn't the problem. Those lights are not actually switched by it, they are switched by the body control module. The dimmer switch just tells the BCM to switch the beams by grounding a signal pin. To determine if the problem is in the BCM you will need to access pin 7 in the C1 connector on the BCM. It has a Black wire with a white stripe. That is the wire that the BCM grounds to activate the high beam relay.
To test it you just need a simple test light that is connected to a good ground.

To get to it remove the trim panel on the left end of the dash, look in there and you will see an electrical connector on the top of the BCM. Next go under the dash and remove the push pins holding the insulator cover over the foot well on the drivers side Pic 3.
Now use a trim stick to remove the trim ring around the ignition switch then remove the center stack trim panel Pic4. Next you remove the screws and pins for the trim panel under the steering column Pic5. Now you can look up in and see the connectors on the bottom of the BCM.
The connector you need has 50 pins in it and will have 5 orange wires in it with 3 of them right next to each other. I cannot remember if that is the side connector you can see from the side cover or the bottom large connector. But if you look for all the orange wires that is the one. Now look for the Black wire with white stripe. It will be pin 7 and between a solid black wire and a Dark Green wire with white stripe.
The test is simple, take the grounded test light and with the key on touch it to that wire. If the high beams come on all of the rest of the high beam parts are good. But you are not getting the control signal from the BCM. The solution is to replace and reprogram the BCM.
For that you need a dealer scan tool and access unfortunately. Because the dash indicator comes on for high beam we know the switch is working and the BCM is getting the signal to select high beam, it just isn't doing it.
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Wednesday, December 9th, 2020 AT 8:39 AM (Merged)
Tiny
CARADIODOC
  • EXPERT
This system is full of computer controls, so you're limited in what you can do without a scanner. While your observations don't point to blown fuses, lets not overlook the two for the high beams. Use a test light to check the two fuses under the hood. They have small test points on top. Turn the head lights on to high beam, then check the voltages on those two fuses. We're looking for 12 volts on one test point and 0 volts on the other one, for each fuse. That indicates they're blown.

For the benefit of anyone else researching this problem, here's a link to an article on how to use a test light:

https://www.2carpros.com/articles/how-to-use-a-test-light-circuit-tester

If you find 0 volts on all four test points, the high beam relay isn't being turned on by the Body Computer.
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Wednesday, December 9th, 2020 AT 8:39 AM (Merged)
Tiny
CARADIODOC
  • EXPERT
Hi Steve. I'll let you handle this. Holler if you need me.
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Wednesday, December 9th, 2020 AT 8:39 AM (Merged)
Tiny
DONALDPIERCE73
  • MEMBER
They were working on the old switch but wouldn't shut off unless you found the right spot on the lever to stay, but would always kick back on. So the switch isn't the problem with it? You think it is in the BCM?
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Wednesday, December 9th, 2020 AT 8:39 AM (Merged)
Tiny
STEVE W.
  • EXPERT
If they worked with the old switch but now don't but the hi-beam indicator is working you will need to test to see if the switching signal is getting to the relay, also test the high beam relay. To be sure it is working. A slightly easier way to do that as you say the were working would be to pull the relay and use a test light to battery positive to the E20 terminal in the relay socket. If that turns on the light the switching signal is there. Then you need to figure out if it's voltage to the relay on pins G19 and 20 or if as Doc mentioned there is a fuse or bulb issue.
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+2
Wednesday, December 9th, 2020 AT 8:39 AM (Merged)
Tiny
JOHNMEVITT
  • MEMBER
  • 2007 PONTIAC GRAND PRIX
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 50,000 MILES
My low beam headlights have quit working as well as my remote keyless entry. The tire pressure monitoring system reads 128 psi in every tire. The latter two problems are less important id just like to know how to fix the headlight problem. Ive checked all fuses and the headlights themselves.
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Wednesday, December 9th, 2020 AT 8:39 AM (Merged)
Tiny
MMPRINCE4000
  • EXPERT
If fuses are OK, then check the relay. High amp draw items will use a relay. It should be in the engine compartment fuse/relay box.

Another possibility is the headlight switch.

The remote may just be a bad battery in the remote.

Most Advance Auto Parts stores have a remote tester for free.
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Wednesday, December 9th, 2020 AT 8:39 AM (Merged)
Tiny
RVELASCOJR
  • MEMBER
  • 2006 PONTIAC GRAND PRIX
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 55,000 MILES
I checked the fuses and they are fine. Is there another part I should check in the fuse box?
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Wednesday, December 9th, 2020 AT 8:40 AM (Merged)
Tiny
DL AUTOSHOP
  • MEMBER
Hello, I'm Danny.

Yes, in the under hood fuse box you should check the lo beam relay. Here is a tutorial showing how to test a relay:

https://www.2carpros.com/articles/how-to-check-an-electrical-relay-and-wiring-control-circuit

I've attached a picture below showing its location on your car. The relay is in location 35 and I circled in red. Hope this helps and thanks for using 2CarPros.
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Wednesday, December 9th, 2020 AT 8:40 AM (Merged)
Tiny
KATBONDWALKER
  • MEMBER
  • 2006 PONTIAC GRAND PRIX
  • 3.8L
  • V6
  • 2WD
  • AUTOMATIC
  • 103,000 MILES
After replacing the driver side headlamp, it still doesn't work. Put meter on it and it reads 10 volts. The other side, which is still working reads 12 volts. 1. Will the relay cause this problem? 2. Wouldn't the bulb still work, dimly, at 10 volts?
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Wednesday, December 9th, 2020 AT 8:40 AM (Merged)
Tiny
SCGRANTURISMO
  • EXPERT
Hello,

Yes, it should. In the diagrams down below I have included the wiring diagram of the headlight circuits for your vehicle and a guide on how to track down unwanted resistance in an automotive electrical circuit with the voltage drop method. This guide will allow you to track down where the other 2.6 volts are being dropped at in the circuit before it reaches the headlight. You will need to use a Digital Multi-meter [DMM] to go through this guide, so here is a link below explaining how to use a DMM, if needed:

https://www.2carpros.com/articles/how-to-use-a-voltmeter

Please go through these guides and get back to us with what you are able to find out.

Thanks,
Alex
2CarPros
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Wednesday, December 9th, 2020 AT 8:40 AM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Good morning,

1. No, if it was the relay, both sides would not work.

2. It may depending on the bulb. The fact you only have 10 volts tells me you have a wiring issue.

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

I attached a diagram for you to view. Re test the voltage on the yellow wire.

Roy
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+1
Wednesday, December 9th, 2020 AT 8:40 AM (Merged)
Tiny
KATBONDWALKER
  • MEMBER
It was the #3 fuse. Somehow, I missed it in the fuse box under the hood. Thank you. The diagram was very helpful.
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Wednesday, December 9th, 2020 AT 8:40 AM (Merged)

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