5V supply: Diagnostics
WARNING: This page is about a different car, the 2001 Saab 9-3. However, it is still accessible from the selected car via links, so may be relevant.
A short circuit on the 5V supply will put the throttle in limp -home mode and can be caused by a fault in the wiring harness or a sensor supplied with 5V. As the two 5V supplies are internally coupled in the throttle housing, no symptoms will appear if there is a break in just one of them.