Turn signal problem with 2008 Chevrolet Cobalt

I am having an electrical problem with my front right turn signal I have not been able to chase down, and I thought I would see if anybody here has some suggestions.

The symptoms are when the headlights are on, either manually or automatically from the daylight sensor, the front right turn signal will not flash, and I get the double speed clicking as if there were a burned out bulb. However, when it is daylight out and the headlights are in daytime running light mode, the turn signal works fine, 95% of the time. Occasionally when the headlights are off the turn signal will not work either.

I have replaced the headlights casing and bulbs, and tried rebuilding the pig tail harness as well. So before I take it to a mechanic and pay to have parts replaced helter skelter till he figures it out, I thought I would ask the community if they have any suggestions.

You need to check the ground and wiring from the headlight to the turn signal with the marker light that is in between them.

Try This Experiment The Next Time It Acts Up . . .
. . . With T-Signals off, cycle the Hazard Lights on and then off. Next, try the Turn Signals. If they work the problem could be in the Hazard Switch. Some GM cars from this era have T-Signal wiring running through the Hazard Switch and sometimes the Hazard Switch creates some puzzling T-Signal problems.

The BCM likely is finding the resistance in the turn signal circuit is higher than it should be, and is causing the blinker to go double speed to tell you there’s a problem.

Ask your tech to measure the resistance from the ground at the socket of the turn signal bulb to chassis ground. It should be a solid connection. If it is greater than 0.1 ohm, or varies when you wiggle the wiring, suspect a ground connection problem.

Is this affecting both turn signals, or just one? If it is just one, simply replacing the turn signal bulb is an inexpensive experiment and may solve the problem. Corrosion in the bulb socket can cause this too. Sometimes cleaning it with a pencil eraser will do the trick.

Whenever working on my car’s electrical system I always disconnect the battery first. Don’t want to create a short circuit or spark which damages some expensive component.