An illuminated Check Engine Light could be caused by a defective VVT-i controller, which changes cam timing for optimal power. Updated parts are available and the repair may be covered under the powertrain warranty.Google+
Car Problem Reports
Scion tC Check Engine Light Due to Defective VVT-i Controller
Scion tC Problem
Average Mileage: 82,783 mi (32,000 mi - 133,567 mi)
Rough idle, high acceleration noise. Need to repair, just happened.
Visitor, 2005 Scion tC, 32,000 mi
dash lights have been on for quite some time. Had a mechanic look at it and was told the camshaft gear assembly needs to be replaced at about $700.00.