Turn signals blinking fast

If the right front signal light of your 2010 GMC Sierra stays on even when the truck is shut off, it could be due to a few possible reasons:
1. Stuck Relay: There might be a malfunctioning relay in the turn signal circuit that is causing the right front signal light to remain illuminated. A stuck relay can keep the circuit closed even when the vehicle is turned off. In this case, you may need to have the relay replaced or repaired.
2. Faulty Wiring: It's possible that there is a wiring issue in the turn signal circuit, causing a constant power supply to the right front signal light. This could be due to a short circuit or a damaged wire. Inspecting the wiring harness and connections for any signs of damage or loose connections would be necessary. If a faulty wire is found, it may need to be repaired or replaced.
3. Malfunctioning Switch: The turn signal switch itself could be defective or stuck in the "on" position. This can cause the right front signal light to remain illuminated regardless of the vehicle's status. Replacing the turn signal switch might be necessary if it is determined to be the cause of the issue.
To pinpoint the exact cause and resolve the problem, it is recommended to have a qualified mechanic or an automotive electrician inspect your GMC Sierra. They will have the expertise and necessary tools to diagnose the issue accurately and carry out the required repairs.

Hey Ronald, Try reseating the LED Bulbs. Depending of the bulbs a polarity change might cause them to flicker faster.
The original bulbs were working off a flasher or relay already. Put Hazard signals On see if the same thing happens. Or simply get the original bulbs back in.
You can also try calling the manufacturer of the LED light bulbs with the model number.Let me know what happens.
Good Luck,
JP
PS I have added a link that may help you. https://www.superbrightleds.com/blog/led-turn-signals-blinking-too-fast-hyperflashing/275

Instead of that, see if you can get an electronic flasher unit for your vehicle that does not depend on the turn signal light load (amps) to control flashing speed. This is much simpler than splicing things into wires.

One of the bulbs is not working. Check and fix.

check all wires for a short to ground

The relay is either under the hood in fuse box or in fuse box on leht side of dashA thumbs up would be greatly appreciated if this answer is helpful to you.

replace the bulbs in the tail light, they are 2 stage, one for parking light and one for brake/signal

if one side is flashing faster than another then check the side that blinks fast because you have one of the bulb blown on that side

Sounds like you need to replace the drivers brake/tail light.

This simply means that the front driver side turn signal bulb has failed. Replace it.