On the V6 the temp gage sender is the firt to check.Its on the X tube casting on the water outlet from the cyl heads,early cars have a single pin connection,later 2000 have two,take off the connector and with ign on ,ground the connection and watch for needle deflection on the gage.If no movement more chance its the gage,if it moves then the sender is shot.PS the ref to the 'spark plug sender' on the air intake is the intake air temp sensor but I assume we are talking coolant temp gage here!
