On 2.7L and 3.5L V6 engines, this procedure can only be done with the engine removed. Begin by relieving the fuel system pressure and disconnecting the cable from the negative battery terminal. Drain the cooling system, then remove the upper and lower intake manifolds. With the vehicle raised and supported properly, disconnect the front oxygen sensors and the catalytic converters. Disconnect the CHT sensor, catalytic converter monitor sensor, and camshaft position sensors. Remove the camshafts from the cylinder head to be removed, and where applicable, disconnect bolts or clips that secure wiring harnesses or ground straps to the cylinder heads. Remove the exhaust manifold(s) and any additional components that might interfere with cylinder head removal. Remove the hoses and any electrical connectors from the coolant bypass tube, then remove the two fasteners securing the coolant bypass tube. Loosen each cylinder head bolt, one turn at a time, following the reverse order of the tightening sequence, and when all cylinder head bolts are loose, remove and discard them, ensuring new torque-to-yield cylinder head bolts are used during installation. Remove the cylinder head from the engine block and place it on a workbench. The mating surfaces of the cylinder head and the block must be perfectly clean before installing the cylinder head; clean the surfaces with a scraper, being careful not to gouge the aluminum. Check the mating surfaces for nicks, deep scratches, and other damage, removing slight imperfections carefully with a file, while excessive damage may require machining or replacement. If warpage of the cylinder head gasket surface is suspected, use a straightedge to check for distortion, and if the gasket mating surface is out of specification or severely damaged, consult an automotive machine shop for advice. Clean the mating surfaces with a clean shop towel and brake system cleaner, ensuring that the two locating dowels are in position in the cylinder block and that all cylinder head bolt holes are free of oil, corrosion, or other contamination. Install new cylinder head gaskets on the block, over the locating dowels, and carefully install the cylinder heads, taking care to prevent damage during the process. Install new cylinder head bolts and turn down by hand until snug, then install the rest of the parts in the reverse order of removal, tightening fasteners. Change the engine oil and filter, then fill and bleed the cooling system, and finally, start the engine and check for leaks.