2001 Kia Optima SE, 2.5 V6
:lol: Both the input speed sensor and the output speed sensor are located below the air box (Air cleaner) on the top of the transmission. They are very easy to replace. If your ECM reports a P0715 code its likely the input speed sensor if it reports a P0720 its likely the output speed sensor. Although they could each trigger the opposing codes. Its best to test the sensor using the processed outlined at Kiatechinfo Sign up for a free account and look under DTC (Default Trouble Codes) You will also want to check the connectors for broken or deteriorated wiring and test the connectors as outlined in the same section. After Replacing the Sensors You MUST Reset and reprogram the base line for the TCU (Transmission Controll Unit) To do this disconnect the negative battery cable for 10 or more seconds, then reconnect the cable and secure it. Get in and start the vehicle and drive it at a slow speed allowing it to shift into all 4 gears, slow the vehicle to a stop and accelerate at moderate speed allowing it to shift into all 4 gears, slow the vehicle to a stop, accelerate at a high rate of speed (FLOOR IT) allowing it to shift into all 4 gears. Enjoy your newly repaired transmission. As a side note in my experience if the TCU is not reset the transmission will exhibit the same symptoms as before but will not set a trouble code.