2003 Yaris High Alternator Voltage

[drcurzon]

Hi There,
I have a 2003 Toyota Yaris.
The battery warning light is on on the dashboard, and the alternator is producing around 17v. I've had the alternator checked, and it seems to be okay.
The only things I can think of are that either:
- The regulator has failed in the alternator
- The car isn't telling the alternator to stop increasing voltage

There is a blue wire connecting to the alternator that I believe goes to the engine management connector, could it be that the wire between the alternator and ECU has broken?

Many thanks in advance, Daniel.