you should only access the TPS either to install a new one and adjust it, or just adjust it...the best/cleanest/trouble-freest is to remove the throttle body: pinch off a couple of coolant lines, disconnect some cables and work on a bench...the other way, less clean is to loosen stuff, hose clamps, and try to twist/wedge to get at the screws...not pretty...make sure you don't strip the screws... 0.63-0.73 volts is specs...
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