The announcement leaves Baidu searching for a global partner to help meet its lofty goal of making self-driving cars a reality for consumers by 2018. The tech company explained to Reuters that it's using Ford vehicles for testing now. Baidu already has ties to the US-based automaker as the two both invested in Velodyne, a company that makes LIDAR sensors that are essential for autonomous vehicle navigation. Ford also has plans to put self-driving cars on the road via a ride sharing service by 2021.

BMW China CEO Olaf Kastner told Reuters that the company and Baidu decided to end the partnership after the two parties had a disagreement on how the research project should proceed. "We now have found that the development pace and the ideas of the two companies are a little different," he said. Kastner didn't go into specifics, but he did mention that the split comes after BMW and Baidu developed automatic overtaking technology or the ability for autonomous vehicles to pass other cars at various speeds. That behavior is widely seen as a key milestone in bringing self-driving cars to public roads.

While BMW and Baidu may not be working jointly on self-driving tech itself, they will continue their high-definition mapping effort together. Detailed and accurate maps are also crucial to autonomous vehicle navigation. Back in August, Baidu revealed a self-driving Chery EQ: a much smaller EV that's better suited for the Chinese market. That vehicle can drive around 120 miles before needed to recharge.