Toyota is conducting a safety improvement campaign involving certain models of the 2004-2006 Toyota Sienna vehicles equipped with power rear lift gate struts. The gas struts used to help lift and support the rear power lift gate could wear out sooner than expected. As the gas struts deteriorate, the performance of the lift gate will begin to degrade and the power rear lift gate will operate more slowly than when the gas struts were new.

Toyota Motor Co. said Tuesday it would cover the costs of repairing doors on up to 600,000 Sienna minivans, after learning from consumers that a part can fail, causing doors to shut unexpectedly.