2002 Infiniti Q45 Sport P0720 Code: Vehicle Speed Sensor Issue in RE5R05A Transmission

Model: 2002 Infiniti Q45Sport Fault Code: P0720 Posted: 2011-04-05 16:17

I own a 2002 Infiniti Q45 (F50) Sport with a 4.5L V8 engine and the RE5R05A transmission. I've been consistently receiving a P0720 diagnostic trouble code — Vehicle Speed Sensor A/T — which remains active even after clearing it via OBD-II scanner. The issue persists: the transmission fails to engage 5th gear and defaults to 2nd gear, indicating fail-safe mode activation. I recently purchased part #31935-1XJ0A, an external vehicle speed sensor with a single bolt mount. Based on my observations, it appears to be installed on the top rear of the transmission. However, I believe this requires dropping the transmission for proper access — which is a significant and labor-intensive task. I'm seeking input from experienced mechanics or owners familiar with this specific model and its RE5R05A transmission. Does anyone have hands-on experience repairing or replacing the vehicle speed sensor in this setup? Are there known common failure points or alternative troubleshooting steps? Note: The RE5R05A transmission is shared across several Nissan and Infiniti models, so insights from those vehicles may also be relevant.