Electric/Computer probs with my Frontera

Hey Guys, I have a 2002 Holden Frontera that has been fantastic, up until now. In the last 2-3 months it has been coming up with the check engine and reduced power lights, and the car loses all power and wont go. It still turns over however. I normally turn the car off, and it will start again straight away. I took it to a 4wd park the other day and it happened again, however this time it deicded not work and I had it towed 350km back home. The mechanics can find codes logges suggesting the pedal sensor out of range and electrical throttle control override, but say they still cant find the exact problem. And now of course the car is working again....this is the 4th time its happend though and its very annoying. If you floor the accelerator it hits about 1500rpm....anyone seen or heard of this prob before???