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Greg A
Greg A, Master Troubleshooter
Category: Chevy
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Experience:  Working with Electronics & Cars for 25+ Years
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The headlight on my 2002 impala quit working. All fuses are

Resolved Question:

The headlight on my 2002 impala quit working. All fuses are good and all relays seem to be working. Parking lights still work and daytime running lights still work. What might be the cause?
Submitted: 4 years ago.
Category: Chevy
Expert:  Greg A replied 4 years ago.

Hello & Welcome,

 

Do you have a test light or multimeter that you can do some testing with?

 

Thanks

Customer: replied 4 years ago.
I have a multimeter.
Expert:  Greg A replied 4 years ago.

Hi again,

 

Let's start with the basics. Here is a schematic that shows the DRL relay and a couple of fuses. If you could use your meter to make sure there is power at both sides of each fuse, that would be great.

 

graphic

 

If the DRLs are working, I suspect that the fuse shown on the right is good.

 

By the way, what relays did you check and how did you check them?

 

Thanks

Customer: replied 4 years ago.
I checked the headlamp relay, the DRL relay. I checked them first by feeling and listening to them actuate. Then I switched them out for known good ones of the same type (the horn relay)
Expert:  Greg A replied 4 years ago.

That's good.

 

Did you check for power at both of the fuses I highlighted, with your meter?

 

If so, the next step would be to check for a good ground at the lights themselves, or the sockets, that are shown in the schematics. This would be the Pink wires for the high beams and the Dark Green wires for the low beams.

 

Please let me know what you find.

 

Thanks, XXXXX

Customer: replied 4 years ago.
there is power at both fuses. I am not sure where the grounds are. I am going to look. All the parking lights work, it is the headlights, hi beams and front daytime lights that are not working.
Expert:  Greg A replied 4 years ago.

OK - You said in your first message that the daytime running lights were working.

 

Is that correct?

 

Do the low beams work?

 

I would check the ground wires at the headlight bulbs themselves.

 

thanks

Customer: replied 4 years ago.
Sorry about that. The daytime running lights are not working (Hi beams and Low-beams are not working. All other lights are working. It appears that I am getting a weak ground on the pink and dark green wires at the bulb. I have an analog meter and testing the wire to a positive source and the needle barely moves off 0 volts.
Expert:  Greg A replied 4 years ago.

Hi again,

 

If you are using the positive source as your reference (connecting your "common" lead of the meter to 12 volts), that means that power is making it through the light bulbs, but there is no path to ground.

 

The ground is provided through the Hi / Low beam switch, and then the Headlight relay, as shown in the schematic below.

 

graphic

 

When you try to select the high beams, does the indicator come on in the dash?

 

Thanks

Customer: replied 4 years ago.
No, no indication of the Hi beam light. I also switched to the ohmeter seting and checked the pink and dark green wires at the bulb and got very little if no reading. Do you think the hi/low switch is the cause?
Expert:  Greg A replied 4 years ago.
I wouldn't condemn the switch yet. I would check the headlamp relay first, if you have not checked it yet.
Customer: replied 4 years ago.
I already swaped the relay with a known woring one (horn relay is the same)
Expert:  Greg A replied 4 years ago.

Hi again,

 

What bothers me is that the DRLs are not working AND the headlgihts are not working too. That kind of tells me that the DRL relay is not turning on, and that is controlled by the Body Control Module (BCM).

If the DRL relay was closing, then both high beam lights would be connected in a series configuration, and the 12 volts would be divided between them. That is what the schematic shows. I am wondering of the BCM is functioning properly.

 

I am also assuming that you are using the light switch to try and turn on the headlights - is that correct? That also sends a signal to the BCM which is supposed to close the headlamp relay.

 

You also have a "flash-to-pass" function of the hi / low beam selector, which the schematic shows would bypass the headlamp relay. This is kind of a middle position on the switch. Does that work (flash the hi beams)?

 

Thanks

Customer: replied 4 years ago.
Yes, I am using the light switch to turn on the lights and the "flash to pass" does not work either. This is stumping me too.
Expert:  Greg A replied 4 years ago.

Yep - this is freaky.

 

Let me just verify that we are talking about the same relays.

 

Here is the diagram for the DRL relay location.

 

graphic

 

Here is the diagram for the Headlamp Relay location. I/P means Instrument Panel (or dash).

 

graphic

 

As an experiment, you could use a jumper wire to connect one of the headlight ground pins (pink or dark blue as mentioned above), to make sure the bulbs actually work.

 

Let me know about those relays.

 

Thanks

Greg A, Master Troubleshooter
Category: Chevy
Satisfied Customers: 6054
Experience: Working with Electronics & Cars for 25+ Years
Greg A and other Chevy Specialists are ready to help you
Customer: replied 4 years ago.
Those are the same relays. It took a while to find the headlight relay behind the left hand fuse block! Thanks for your help. I will try this tomorrow. It is late and I have to work in the morning. Please reply back one more time so I can accept and pay and I will get back on line again tomorrow. Thanks again for the help.
Expert:  Greg A replied 4 years ago.

No problem. I should be here tomorrow.

 

Thanks, XXXXX

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