General Motors has an important -- and deep-pocketed -- new partner in its race to develop self-driving cars. A fund related to the SoftBank Group of Japan has pledged to invest $2.25 billion into GM Cruise Holdings, the Detroit automaker's autonomous technology division.

"Teaming up with SoftBank adds an additional strong partner as we pursue our vision of zero crashes, zero emissions and zero congestion," said GM Chairman and CEO Mary Barra, in a prepared statement.

As part of the deal, General Motors has itself pledged to invest a further $1.1 billion into GM Cruise when the deal with SoftBank is consummated.

According to GM, the investment will come from The SoftBank Vision Fund in two stages. SoftBank will invest an initial tranche of $900 million, and it has pledged a further $1.35 billion when GM's Cruise driverless vehicles are "ready for commercial deployment," having received regulatory approval.

Once completed, the deal will mean that SoftBank Vision will own a 19.6-percent stake in GM Cruise, at an estimated value of $11.5 billion. 

SoftBank Vision, a technology investment fund, also has significant stakes in ride-hailing firm Uber, as well as Santa Clara, CA chipmaker and Tier One automotive supplier Nvidia. 

As disclosed in a GM statement, the companies are anticipating commercialization at scale beginning in 2019, but it's not clear yet what that means. It appears highly unlikely that GM will be able to push for retail-saleable new vehicles with fully automated drive tech by anywhere near that timeframe, but a ride-hailing service or other select-location deployment may be possible.

GM has been publicly testing prototype versions of its Chevrolet Bolt EV electric car equipped with Cruise's automated driving hardware in cities like San Francisco.