GM recommends that the battery remain within 40 degrees of horizontal during removal and installation to prevent spilling electrolyte out of the battery case atmospheric vent. 2005 Grand Am models equipped with the OnStar package require special attention when disconnecting the battery. The system retains a residual charge once the main battery is disconnected in order to preserve the OnStar functionality if main battery power is lost during an accident. Discharge this reserve power by opening the driver door with the ignition switch in the "Off" position. Failure to do so will cause the OnStar to activate and discharge its backup battery. Once activated, the OnStar cannot be deactivated and it will deplete the backup, making it necessary to replace the backup battery since it cannot be recharged. Before you disconnect the battery, make note of your radio presets and radio security code if applicable.
Turn all of the vehicle accessories off. Turn the ignition switch to the "Off" position and remove the key. Open the driver's door to discharge the residual power, then pop the hood and close the door.
Locate the battery at the driver-side front of the engine compartment. Using a ratchet and socket, loosen and remove the negative terminal bolt, and disconnect the cable from the battery. Lay the cable aside to avoid accidental contact with the battery.
Remove the positive terminal bolt. Using a ratchet and socket, remove the battery retainer bolt and retainer. Lift the battery up and out of the battery tray. Be mindful of the angle on the battery as you move it clear of the body member that passes over the corner of the battery.
Lower the new battery into position on the battery tray, and again be aware of the angle on the battery. Install the battery retainer and retainer bolt, then tighten it securely. Clean the battery cable terminals as necessary, using a wire brush to remove any corrosion that may prevent a good connection during reassembly.
Install the positive cable and terminal bolt on the positive battery terminal. Using a foot-pound torque wrench and socket, tighten the terminal bolt to 11 foot-pounds. Exercise caution while tightening the terminal bolts to avoid over-tightening the bolt and causing permanent damage to the internal threads of the battery.
Install the negative battery cable and terminal bolt on the negative battery terminal, and tighten the bolt to 11 foot-pounds.
