flashing enginre check light

P0306 will not relate to an engine thermostat. However, this is showing evidence of engine misfire. This will cause the light to flash. I do not now which 3.0L V6 engine you have -- the OHV or SOHC engine -- either way, start by checking spark plugs, spark plug wires and / or coil boots if equipped depending on the engine you have. Testing may be required to check for ignition system issues, fuel system issues, base engine compression. Note: DO NOT continue to drive until this concern is resolved! A flashing check engine light indicates an active misfire is occurring and fuel is being dumped into the exhaust system -- which will damage exhaust components like the catalytic converter! This is very important to avoid.