Wiring diagram headlights

I saw this question hanging around since yesterday, so thought I would take a crack at it. I remembered that Jeff has access to data where grounds are, so thought I would try. I see he has answered.

Jeff Armer Aug 18, 2023
It's not a ground issue, driver side headlamp grounds at same place (G201) underneath the dash .

Headlamps
The headlamps may be turned on two different ways. First, when the driver places the headlamp switch in the HEADLAMP position, for normal operation. Second, with the headlamp switch placed in the OFF position, for automatic lamp control (ALC). During ALC, the headlamps will be in day time running lamp (DRL) operation in daylight conditions, or low beam operation in low light conditions. The LH HDLP and RH HDLP fuses, supply battery positive voltage from the under hood junction block to the left and right headlamps. The circuit continues through both low and high beam lamps, then back to the under hood junction block. The low beam and high beam circuits continue to the headlamp switch. The low beam and high beam circuits also provide the body control module (BCM) with both low and high beam inputs. The headlamp switch includes the dimmer switch and the flash-to-pass switch. When the headlamp switch is placed in the HEADLAMP position a path to ground is provided. Ground is provided at G201. Depending on the position of the high/low beam switch, either the low or high beam circuit will now have power and ground.

G201
On the left side of the I/P, near the fuse block

I found this, as Jeff says, not a normal ground near the light unit because it is computer controlled.

What is the ground wire for the headlight on a 2000 Pontiac

JustAnswer https://www.justanswer.com > Pontiac Problems
Mar 21, 2017 - What is the ground wire for the headlight on a 2000 Pontiac Grand Am? It only has three wires. two blue and one red or pink.

1 answer · Top answer: Hi, my name is ***** ***** body control module controls the ground for the headlights, ...

..

PAWEL IS A BOT. HE POSTS GENERIC ANSWERS. AND OVERLAYS NAME OF YOUR CAR. 82 GENRIC ANSWERS HIM
AND LIES ABOUT IGN SWITCH.
NOW YOUR CAR.! FACTS, ONLY, 1 CAR
LEARN TO USE THE DMM , CORRECTLY;
HEAD LAMPS ON.(SWITCH) NO KEY IS NEEDED FOR HL.
IS DRIVER LEFT OR RIGHT,? IN USA LEFT.
IS HIGH AND LOW BEAMS DEAD LEFT? No TOLD AT ALL.
PUT METER BLACK LEAD TO THE BATTERY NEG LUG
THEN PROBE RED TO ALL WIRES OF DEAD LAMP 1 BY 1.
12VDC IS GOOD 0 BAD
IF LAMP GROUND PIN READS 12VDC <<< GROUND FAILS.

LEFT LAMP USES GROUND LUG G101. IF R

CAR HAS DRL. SO DRL AND MANUAL LAMPS FAIL
HIGH , LOW , AND FLASH HIGH>? NOT TOLD
DOES ENGINE RUN? OMG NOT TOLD.
THIS CAR RUN HL RELAYS BY BCM CONTROLLER BRAIN


FUSE ARE ON THE OUTPUT OF ALL HL RELAYS
SO IF ALL FUSES INPUT(TOP) ARE DEAD,THAT MEANS
BCM IS FAILING. OR THE SWITCH TO IT.
OR FUSES BLOW TO BCM
WE SCAN THE PCM/BCM TO SE WHY.


HEAD LAMPS ON THE 4 FUSES ALL 4 RIGHT SIDE ARE
12VDC, IF NOT BCM IS MESSED UP, OR RELAY DEAD.
HE LOW BEAM RELAY RUNS BOTH SIDE
SAME WITH BEAM. A RELAY FOR IT.
DRL HOT ONLY IN DRL MODE.
DRL; HAS A SUN SENSOR (AUTO MODE)


BOTTOM HERE IS HEAD LAMPS.SIDE.

HEAD LAMPS ON USA WORK EVEN KEYOFF
SO DOES BCM TO DO THAT, MAIN BATTERY NOT DEAD

If this fuse box diagram below is correct you have a fuse for left low beam head light and another fuse for right low beam head light and a third fuse for both the high beam headlights. If the fuse is good for the right I think I would take the left low beam head light and put on the right side and see if it works on the right side. If you think you got the wiring correct. It may be the bulb is bad from the wires which shorted out. A voltmeter or test light to the socket would save some time switching the lights. I have had the socket bad before and had to change the bulb socket.
https://fusesdiagram.com/ford/fuse-box-diagram-ford-taurus-2000-2007.html

Have you checked the relay in the circuit. You really need a schematic of the wiring diagram. Electrical can be tricky without the wiring diagram.

seems you have several different problems. High beam working and no low beams=dimmer switch is bad. Reverse lamp not working=bulb socket bad,wiring broke,bad ground at back
Brake light on drivers side stuck on=brake light switch

Both your low beam and your high beam is protected by the same fuse, so it makes sense that the fuse is OK if the high beam is working on the passenger side. There are 3 fuses for the headlamps. Fuse #13 in the Battery Junction Box (20 Amp). If this fuse is blown, the headlamp relay will not have any power and neither high nor low beam on either side will work (you will have no headlamps at all) Then there is Fuses #2 and #3 (15 Amp) in the Battery Junction Box. #2 goes to the left low and high beam and #3 goes to the right low and high beam.
The headlamp switch uses a SINGLE CIRCUIT to control BOTH sides at the same time, so if one side works, the switch cannot be the problem. The headlamp relay provides power for fuses #2 and #3 and we already ascertained that these fuses must have power since we have working lights on both sides, so the relay cannot be the problem. A replacement bulb has already been tried, so that pretty much leaves us with a bad lamp socket. (Most likely cause) or a bad connection at splice #S122, which is located in the main wiring harness near the breakout for the left headlamp. (RED/BLACK wire)

For Audi A4 the fuse box is located on the left side of dashboard behind a plastic cover (for left hand steering wheel vehicle). On inner face of the plastic cover you will find the fuse diagram.
First fuse on first row from left upper corner is Fuse Nr.20 = F20 (15A) - RH headlamp low beam, headlamp adjustment.
First fuse on second row from left upper corner is Fuse Nr.21 = F21 (15A) - LH headlamp low beam, headlamp adjustment.

high beam or low beam? or both of them on one side.

• One low beam headlamp is inoperative

• Central junction box (CJB) fuse 23 (10A) (RH headlamp).
• CJB fuse 25 (10A) (LH headlamp).
• Circuitry.
• CJB.

• Go To Pinpoint Test C .

• One high beam headlamp is inoperative

• Circuitry.
• Headlamp assembly.

• Go To Pinpoint Test D .

• The high and low beam headlamp is inoperative on one side

• Circuitry.

• REPAIR ground circuit 57 (BK).

• Headlamp switch
• Multifunction switch
• Vehicle Security Module

• Central junction box (CJB) fuse(s):
  • 17 (15A)
  • 23 (10A)
  • 25 (10A)
  • 35 (20A)
  • 40 (20A)
• Circuitry
• Headlamp bulbs
• Daytime running lamp (DRL) relay

The low beam headlamps have a seperate fuse for each lamp in the central or underdash fuse panel.
The right headlamp is fuse fuse 26 (10amp) and the left is fuse 28 (10 amp). These fuse are hot only when headlamps are on so you need to test them with a test light with headlamps on. If they do not have power to them then concern is either headlamp switch or daytime running lamp relay if your vehicle is equipped with this feature, or a bad multifunction switch.
Power leaves the headlamp switch on the RD/YE wire and goes to multifunction switch. It leaves multifunction switch on the other RD/YE wire The wire will then go thru either a connector c2003 located behind the passenger side air bag behind the dash or to the DRL relay if your vehicle has this feature and leaves there on RD/BK wire to the headlights .