Low battery voltage
Faulty Engine Control Module (ECM)
Engine Control Module harness is open or shorted
Engine Control Module circuit poor electrical connection
Engine Light ON (or Service Engine Soon Warning Light)
These circuit lines are used to control the smooth shifting up and down of A/T during the and acceleration/deceleration. Voltage signal are exchanged between the Engine Control Module (ECM) and Automatic Transmission (A/T) control unit.