Boy that goes to show you how different minds think; Gas, right rear of engine at the bell housing, it fits in an access hole to read the flywheel. If it's a diesel it's in a different spot all together. Fix your city and state, sometimes we ignore Potwin Ks.
IF it's a 1999 year model with the 5.9 24 valve Cummins diesel engine,, the sensor is in the engine block at the base of the engine oil dip stick tube and the starter will need to be removed to replace the sensor!!!