2010 Hummer H3 Owner's Manual - Page 226

9-42 Driving and Operating { WARNING It is dangerous to get out of the vehicle if the shift lever is not fully in P (Park) with the parking brake firmly set. The vehicle can roll. Do not leave the vehicle when the engine is running unless you have to. If you have left the engine running, the vehicle can move suddenly. You or others could be injured. To be sure the vehicle will not move, even when you are on fairly level ground, always set the parking brake and move the shift lever to P (Park). See Shifting Into Park on page 9‑37. If you are pulling a trailer, see Driving Characteristics and Towing Tips on page 9‑70. It features an electronic shift position indicator within the instrument cluster. There are several different positions for the shift lever. P (Park): This position locks the rear wheels. It is the best position to use when you start the engine because the vehicle cannot move easily. Make sure the shift lever is fully in P (Park) before starting the engine. The vehicle has an automatic transmission shift lock control system. You must fully apply the regular brakes first and then press the shift lever button before you can shift from P (Park) when the ignition key is in ON/RUN. If you cannot shift out of P (Park), ease pressure on the shift lever and push the shift lever all the way into P (Park) as you maintain brake application. Then press the shift lever button and move the shift lever into another gear. See Shifting Out of Park on page 9‑38. R (Reverse): Use this gear to back up. Notice: Shifting to R (Reverse) while the vehicle is moving forward could damage the transmission. The repairs would not be covered by the vehicle warranty. Shift to R (Reverse) only after the vehicle is stopped.