Defect
On certain vehicles, a software problem could cause the turn signal telltale to flash at the same speed as when a rear turn signal bulb fails. As a result, you may not notice when a rear turn signal bulb is not working. Canadian regulations require a change in the turn signal flash rate when a bulb fails.
Safety Risk
A turn signal telltale that doesn't work properly could cause you to be unaware when a turn signal bulb fails. Turn signals that don't work may cause a person not to recognize when a driver intends to turn or change lanes. This could increase the risk of a crash.
Remedy
General Motors will notify owners by mail and send a wireless over-the-air software update to eligible vehicles to update the exterior lighting control module software. Alternatively, you may schedule an appointment to have the update performed at a GM dealership.