On vehicles equipped with the "police" option package, one or both of the front lower control arms may fracture. A broken control arm can result in the loss of control of the vehicle, increasing the risk of a crash. Dealers will replace both front lower control arms to correct this concern. The General Motors recall number is 12104.
 
Recalls
Recalls are issued for cars with safety-related defects or problems
2008 Chevrolet Impala
The Front Control Arms May Break on Impala Police Vehicles
Suspension & Steering, August 3, 2012