PWM Fan Control Engineering, Direction, Advise.

We are looking for engineering advise regarding the operation of and acquisition of a PWM fan controller. Automotive. 12v 15a motor. the motor is a GM (General Motors) unit from 1999. the attached wiring diagram is the only information we have regarding the motor's wiring. It is a three (3) wire system, + Red, (-) Black, and signal White. We have been unable to find a three wire controller to power this fan and are looking for engineering advise and direction on where to acquire the appropriate PWM fan controller to operate the motor. When the positive and negative wires are connected to 12v the fan motor is OFF. We would prefer a stock controller but will look to a custom controller if not other options are available. The project will consist of explanations, directions, options, wiring diagrams and is not complete until the equipment is operating completely correctly in our facility. Specific PWM experience required.