P18C9 Code: Meaning, Causes, and Symptoms | OBD2 Codes

P18C9 – Gear Position Sensor Gear Ratio Not Plausible


P18C9 Possible Symptoms


Engine Light ON (or Service Engine Soon Warning Light)


P18C9 Possible Causes


Faulty Gear Position Sensor,Gear Position Sensor harness is open or shorted,Gear Position Sensor circuit poor electrical connection


P18C9 Description


The gear position sensor is a switching transistor mounted to the top of the transmission extension housing. The four wire sensor interfaces directly with the Engine Control Module (ECM). The ECM supplies 5 V to the gear position sensor on a 5 V reference circuit and also provides a ground path on a low reference circuit. The sensor provides a Pulse Width Modulated (PWM) duty cycle to the ECM on two signal circuits that is proportional to the linear and radial position of the corresponding magnet assembly mounted to the shift shaft. The vehicle uses the gear position sensor information primarily for Active Rev Matching and Active Fuel Management. The ECM monitors the sensor signal input for an incorrect neutral condition.