I have the answer, and my Spike is working better than ever. It was the battery pack. Have someone replace the rechargeable batteries with the same or slightly stronger rechargeable batteries. A lady at Fischer-Price suggested I find a hobbyist who likes to solve problems. I took my Spike to the local train store, where a hobby problem-solver examined him in great detail. Everything was working, including the little motherboard inside. He replaced the battery pack. Spike is alive again.