I performed this Google search: "p0705 transmission range sensor circuit malfunction 4runner" and found over 6 hits linking to this forum. Paging though some of them, I found two posts where the person who started the thread came back to post how it was fixed. In one case, they wrote, "Fixed. Bad ground on my left rear tail light. Not sure where P0705 comes in but I'm glad it was simpler than it seemed." The other person replaced the neutral safety switch. Corrosion appears to be an issue in the 3rd link. Many who experienced this error code report various additional symptoms you may or may not be experiencing. Here are a few of the links:
Po705
P0705 Code, then clears up
First issue with my truck, any ideas what's wrong?
Neutral Safety Switch
P0705 Error and bad Neutral Sensor Switch
You'll find more hits if you perform the Google search and click "more results from toyota-4runner.org"
It appears diagnosis is a complex procedure per this link for Toyota service techs:
http://www.to4runner.net/transmissio...0705_-787.html The test procedure involves checking switches, connectors, wiring harness, grounds and the ECM.