OBD2 CAN bus reader scanned P0720 for transmission output shaft speed sensor circuit failure. The check engine light was illuminated, the speedometer was not working and upshifts were slow and sluggish. The green overdrive off light was flashing.The OSS measures driveshaft rotations for spedo and odometer. Shaft RPM also controls shifting. On mine the wiring harness had broken wire. I found a rat's nest under hood and I assume the rat chewed through the cable. It was impossible to get hands up there to repair so transmission had to be lowered to gain access. Once fixed use OBDII code reader to scan bus and clear P720 CEL error. Could also get P0722 or P0731 DTC malfunction trouble readings for Insufficient Input.