Cleared the code and went for a ride. The Fuel Saver light came on, then went off and the CEL came back on. I believe it's the solenoid that could be bad which won't let the engine go into MDS mode. The problem is the solenoid is located under the manifold. I wish there was an easy way to at least verify that it is the solenoid, or a way to get [censored] off the MDS.