Jatco JF011E Stepper Motor Testing

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The Jatco JF011 CVT transmission (referred to by Mitsubishi as the F1CJA and W1CJA) is known to be less than robust.

One of the most common problem areas with the CVT is the stepper motor. Generally when the stepper motor fails you will receive a P1777 error indicating an electrical malfunction with the stepper motor.

F1CJA Valve Body.png

The stepper motor (6) is located on the top side of the transmission valve body and assists in selecting the gear ratio in use by moving the Ratio Control Link (8) which sets the position of the Ratio Control Valve (7).

Stepper motor pinout

The stepper motor is a unipolar two winding type with six wires going into it. Each winding has three wires running into it, with the black wires at pins 2 and 5 being the ground.

To test the stepper motor windings, using a ohmmeter check the resistance between the following pins:
1 and 2 = 15 ohms
2 and 3 = 15 ohms
1 and 3 = 30 ohms
4 and 5 = 15 ohms
5 and 6 = 15 ohms
4 and 6 = 30 ohms

If they are within say 5 ohms either side of these values the stepper motor is most likely OK.

Stepper Motor Movement Tester Schematic

To check the movement of the stepper motor you will need to use a stepper motor controller. As the motor uses six wires, it can be driven in either unipolar or bipolar mode. You can create a simple stepper motor tester using an Arduino Uno, Duinotech XC4492 module and a power supply.