does the engine temp sensor need to be replaced along with the thermostat on 2004 passat
Usually not, unless it's faulty. When was the water pump replaced last?
pump was replace with timing belt at about 98,000 mi
However, the thermo-switch is the radiator that controls the fan is a definite change item at 100K.
Replacing the thermostat and coolant temp sensor at the same time take care of the fault code he's no doubt getting. Otherwise you're guessing, then draining coolant, replacing the other part, refilling and bleeding all over again.
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