2005 Mercedes CLK-Class Owner's Manual - Page 404

Practical hints Replacing batteries in the SmartKey/SmartKey with KEYLESS-GO* If the batteries in the SmartKey or the SmartKey with KEYLESS-GO* are discharged, the vehicle can no longer be locked or unlocked. It is recommended to have the batteries replaced at an authorized Mercedes-Benz Center. Warning! i When inserting the batteries, make sure they are clean and free of lint. SmartKey Replacement batteries: Lithium, type CR 2025 or equivalent. Remove mechanical key 1 ( page 397). i When changing batteries, always replace both batteries. The required replacement batteries are available at any Mercedes-Benz Center. G Keep the batteries out of reach of children. If a battery is swallowed, seek medical help immediately. Batteries contain materials that can harm the environment if disposed of improperly. Recycling of batteries is the preferred method of disposal. Many states require sellers of batteries to accept old batteries for recycling. 1 Mechanical key 2 Battery compartment Insert mechanical key 1 in side opening and push gray slide. Battery compartment 2 is unlatched. Pull battery compartment 2 out of the SmartKey housing in direction of arrow. 402