Ford is issuing a recall for more than half a million vehicles in Canada and some 4.3 million in the U.S. due to a software glitch that may cause trailer brakes not to function and exterior lights to fail.

The recall affects certain models of some of Ford’s most popular vehicles, including some 2021-2026 F-150s, 2022-2026 Super Duty trucks, 2024-2026 Rangers, 2022-2026 Mavericks. Approximately 590,191 vehicles in Canada are impacted.

The company says it will issue an over-the-air software update for the affected vehicles, though customers will also be able to use mobile service or visit a Ford dealer to get the update.

The update will be available for most models starting on March 17, and will be deployed for all vehicles by May, Ford says.

When pulling a trailer, the software issue can cause the trailer to stop communicating with the vehicle, causing the trailer’s stop lamps and turn signals not to light up. In some cases, the trailer’s braking function might also be lost.

The National Highway Traffic Safety Administration said trailer lights or brakes ‌that do not function can reduce the driver’s ability to control the trailer, increasing the risk of a crash.

Ford says a “Trailer Brake Module Fault” message will pop up for drivers and the turn signal indicator will flash rapidly if a vehicle does experience the communication loss.

Ford said it is aware ​of 407 incidents that may be related to the recall ⁠issue, but no accidents or injuries tied to it.