GMC Yukon Denali XL Headlight Assembly
Ways to Diagnose Common GMC Yukon Denali Headlight Assembly Problems
Your GMC Yukon Denali headlight assembly is an essential safety system for driving during the night and under low-visibility conditions. If this component is not working, then you won't be able to see the road clearly at night or in the rain. Make sure that you avoid this inconvenience by troubleshooting any problem that might arise.
Problem #1: One headlight does not work
If only one headlight is not working, then its bulb might have burned out. Bulbs have a limited life that depends on the number of hours they are used and how much vibration they have been subjected to over time. If your vehicle has an incandescent headlight, then the thin tungsten filament inside it might have burned out over time.
Check for a burned-out bulb. If the bulb is alright, inspect the electrical connections-the socket and connecting wires-for corrosion. Tighten any parts in this area that may have loosened over time.
Problem #2: One (HID) xenon headlight does not work
If your vehicle has High Intensity Discharge (HID) xenon headlights installed, then the root cause is different from the one given above. In many cases, this problem occurs for cars that have Daytime Running Lights. You'll know you have this problem when at initial discharge, the bulb turns off after just starting the vehicle or while you're already driving.
This problem could be caused by a bad headlight bulb, a loose bulb, a bad igniter, or a faulty ground connection at the igniter.
Problem #3: Both headlights do not work
If both headlights are out at the same time, then the problem is likely to be electrical. Usually, this is caused by not having voltage to the headlights due to a bad headlight relay, fuse, headlight switch, dimmer switch, or wiring fault. To figure out what's causing both headlights to fail, start by inspecting the main fuse for the headlight circuit and work from there. Also, even after solving the problem, check for other potential problems in order to prevent a recurrence.
Problem #4: Headlights seem dim, or their brightness changes when revving the engine
This is mostly a charging system problem such as a bad alternator or slipping alternator drive belt. Inspect the charging voltage while the engine is idling. If the voltage at the battery is at 13.5 to 14.5 volts, then the charging system is working properly. However, if it is less than 13 volts, then there is something wrong with the charging system.
If the charging system isn't the problem, test the front-end lights and make a list of other possible problem areas. Inspect the parking, fog, and headlights for continuous and sporadic use-if at least one of them is faulty, then the headlight assembly might be affected due to bad wiring.