I have a 2014 ES350 with code P0990 for the transmission with the check engine light on. When driving from gear 2-3 the engine will rev and car will jerk hard. I understand the error code doesn't mean replacing the switch would resolve all issues, but it's a small and cheap part, so it doesn't hurt to try and replace it. I've looked around and couldn't find any good tutorials or any diagrams that helps me access the switch on the transmission. I took out the battery and looked under but couldn't really see much.

 

The TRS, is typically mounted on the transmission housing. In most vehicles, it's positioned near the shift linkage. Once you have clear access, inspect the TRS for any visible damage or wear. Disconnect the electrical connector and remove any retaining bolts securing the switch. Replace it with the new part, securing it in place with the appropriate bolts and reconnecting the electrical connector.