I recently started having problems with the tach on my 2004 Trailblazer. The truck Idles normal but the tach reads 5,6 or 7,000rpms. Then it goes back to normal and then acts up again. I went on several websites and saw many with the same problem but most complaining about the speedometer. Well, just my luck now the speedometer sticks at times not going beyond 50 or 60mph. Sometimes when I come to a complete stop the speedometer shows 20 mph. The sites I visited say that its over $800.00 to fix. Does anyone know a simple remedy? If the battery was disconnected for a few hours would it reset? If there are so many complaints like I saw, why isn't there a recall?