Sorry, but I had that code on my 04. 5. Took it to the dealer and they told me there was a loose crimp on a wire. Almost the exact same mileage when it happened to me. They told me the warranty didn't cover "crimping a loose wire" and I said it shouldn't have ever come loose if it was done right at the factory. Long story short, Check the wires for loose crimps on the wire(s) to the grid heater. If you can't find anything, take it in to the dealer.
Sorry I can't be more helpful.