Some common problems reported by owners of the 2006 Hummer H3 include engine problems such as leaking valves, cylinder head failure and a tendency to run rough. Common electrical problems reported for this make and model include a faulty passlock light that prevents the vehicle from starting.
The most common solutions for leaking valves in a 2006 Hummer H3 is replacing the valves. In some cases, owners had to replace the entire cylinder head. This issue typically occurs around the 80,000 mile mark and costs about $2,500 to repair as of 2015.
The faulty passlock light, which is due to a weak ignition switch, is part of the H3's anti-theft system. This system automatically resets every 10 minutes, at which point it is drivable again.