If I can jump in here it sounds like the BCM or combination flasher has gone out due to a voltage surge when the battery was replaced. I would do a CAN scan to confirm the issue. To be sure lets do a CAN scan which is the future of automotive repair you can get a CAN scanner from Amazon for about $50.00. here is a video to show you how:
Here is the flasher and BCM location and the blinker wiring diagrams so you can see how the system works so you can check it out.
The flasher is mounted to the back side of the multi-function switch. To gain access, the upper steering column cover must be removed. The flasher can be removed by pulling it forward. The flasher is serviced separately from the multi-function switch. The flasher is black in color for ease of identification.
The flasher is mounted to the back side of the multi-function switch. To gain access, the upper steering column cover must be removed. Push the flasher toward the rear of the vehicle. The flasher is black in color for ease of identification.
Check out the diagrams (below). Please let us know what you find. We are interested to see what it is.
Images (Click to enlarge)
Friday, June 19th, 2020 AT 10:18 AM