Care is needed here, due to the sophisticated timing system; the wrong move often results in terrible damage to the engine; only professionals should try this and if you are in doubt, do contact a professional. Quite as importantly, any work accomplished should be checked again before the engine is run. To make sure that the magnetic timing wheels on the camshafts do not accidentally encounter magnets or magnetic fields, the valve covers must be taken off; in this case, the wheels must be replaced. Each of the camshafts' timing chain can be easily removed when using the right tools; however, it is only possible to do it if, at least, the timing chain cover and the chains are removed. First remove the negative battery terminal and then drain the engine oil and coolant, after that remove the drive belt, air filter housing, resonator and last but the intake manifold. Pull all wires and vacuum hoses off the cylinder heads, color-code them to install them back again, and then take off the ignition coils along with the spark plugs; color-code the coils too. Once you have lifted the valve covers turn the crankshaft until the #1 piston is on the exhaust stroke and the camshaft phaser marks line up. Locate the camshaft phasers to the timing chains for future installation then using a specific tool to hold the tensioner the camshaft phaser lock tool is inserted. The oil control valves need to be loosened and then detached from the camshafts, the intake and exhaust phaser needs to be unscrewed from the camshafts with the phaser lock still engaged. Turn both camshafts anti-clockwise until they are in a position that is believed to be mid-way, remove the sheer bolts and the caps and lift the camshafts upwards. Use and remove the rocker arms and hydraulic lash adjusters, clean the camshaft bearing surface and lobes, if there is any damage MARK 10 and replace all defective parts. For build to be installed, the hydraulic lash adjusters should be dipped in clean engine oil, while both the rocker arm contact points should be greased appropriately; the installation of camshafts on the cylinder head should also be done at the right angle. Move to the next step and tighten the bearing caps, check their alignment and then fit the phasers and oil control valves; all the assemblies should be rightly tightened. Last and final step is to turn the engine for alignment marks and other reassembly and installation process, which will be in the reverse order or removal.