P2135 code on '06 S80

[litewait]

06' S80 138k miles, stalled once, got it running again. I've put 50 miles on it since no issues.

Pulled the codes and I am getting P2135 $0710 Throttle Position.

I am in fix it or sell it mode with this vehicle. Scared to death to take it to the local dealer since a few years back my son took it in for a normal service oil/change etc. and they charged him $295!

I do have a local guy that I trust, but not sure diagnosis of this is over his head.

My reading suggests its either the position sensor, ETM, or (ugh) throttle body.

If the repair is greater that $1000 probably will think about selling it.

UPDATE: It seems if its the position sensor you have to replace the whole throttle body, can that be???????

UPDATE AGAIN: My son drove it to my house now the code cleared?  How can that be?

Advice please?