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Dan
Dan, Auto Service Technician
Category: Car
Satisfied Customers: 3490
Experience:  GM ASEP A.A.S. 14 years GM experience. Mark of Excellence and Professional Guild awarded.
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2001 yukon: will not come on automatically or manually at times

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My 2001 yukon headlights will not come on automatically or manually at times. but bright lights will work. Than the headlights will sometimes come on after a short period of time. all relays and fuses are fine. what is wrong with it?
Do they work if you alternate between high and low beams repeatedly?
Customer: replied 9 years ago.
No. high beams will work. low beams will not. but this only happens about every other 3 times i use it. Sometimes the low beams come on. Sometimes they dont. It also varies on how long it will take for the low beams to come on.
Have you ever replaced the multifunction switch (high beam switch included with the wipers, hazards, turn signal)? They can do strange things and supply power to certain circuits but none to others.
Customer: replied 9 years ago.
no i haven't. but three mechanics looked at it and both said they don't think thats what it is. Also, one of the mechanics has the same vehicle and it has never happened to him and the previous owner never had this problem. it makes no sense.
Customer: replied 9 years ago.
Also. i have a 2001 Tahoe as my cop car and that problem never seems to occur either. One mechanic tore apart the malfunction switch and noticed nothing out of ordinary.
Headlamps Inoperative - Low Beams

Step

Action

Yes

No

Schematic Reference: Headlights Schematics

1

Did you perform the Lighting Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check - Lighting Systems

2

Turn ON the headlamp switch.

Do the headlamps operate normally?

Go to Testing for Electrical Intermittents in Wiring Systems

Go to Step 3

3

  1. Disconnect the headlamp dimmer switch connector C201C.
  2. Turn ON the headlamp switch.
  3. Connect a fused jumper wire between the headlamp dimmer switch low beam signal circuit of connector C201C to a good ground.

Do the low beams illuminate?

Go to Step 4

Go to Step 6

4

Connect a test lamp between the ground circuit of the dimmer switch and battery positive voltage.

Does the test lamp illuminate?

Go to Step 5

Go to Step 7

5

Inspect for poor connections at the engine wiring harness junction block and the dimmer switch. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 9

Go to Step 8

6

Repair the open in the headlamp dimmer switch low beam signal circuit between the engine wiring harness junction block and the dimmer switch. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 9

--

7

Repair the open in the headlamp dimmer switch ground circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 9

--

8

Replace the headlamp dimmer switch. Refer to Multifunction, Turn Signal, and Hazard Switch Replacement - On Vehicle in Steering Wheel and Column - Tilt or Multifunction, Turn Signal, and Hazard Switch Replacement - On Vehicle in Steering Wheel and Column - Standard.

Did you complete the repair?

Go to Step 9

--

9

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 3

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