All of the sensors used on the "LS" type engine use a 5 vdc signal reference with a two wire connector. During many swaps, they leave the "LS" oil pressure gauge in the block at the top rear, and keep the wires into the PCM. There maybe logic built into the PCM to "Kill" the engine after a success start ( * ) while driving down the road, if oil pressure is lost. Nothing in GM's eSI says so, but maybe used in later models of updated with software. Other choices during a swap, is go to the un-use oil cooler plate over the oil filter, remove it, determine the correct angle, center punch a starter location then drill & tap to 1/8" NPT that the old school oil pressure switch will screw into.
GM makes a sealant P/N 12346004, that is a white viscous liquid with PTFE and is ok for use when re-using a sensor that requires block ground. It is listed for this a many other sealing jobs from frost plugs to head bolts, but still provide ground for the sensor. New sensors come with a sealant on the threads and require no more attention.
As for coolant gauge sensor in the cylinder head for the 95,96,97 5.0L truck vortex engine is a little confusing. They have a oblong weather pack connector, but use only the wire right of the connectors clip. Replacements come with two wires, but the OEM uses only that one wire. Some replacement have one wire, but terminate at a two wire connector. If the coolant dash gauge starts at 100 - 220F, the resistance is 85 ohms = 220F, 600 ohms = 100F.
(Note: The ECT on "LS" engines, run 74 ohms = 302F, 100700 ohms = -40F) Uses a rectangular connector W / 2 wires. So plugged, shows -40F, grounded reads full hot on scan tool)
For diagnostics, the easiest thing to do is; key on-engine off, disconnect. The dash coolant gauge should over-peg 220F. Using a jumper wire to ground on the same sensor wire, should peg the gauge to below 100F.
Short of no-one having the factory "J" tool, a potentiometer wired with leads to center wiper, then one end of the pot, can be connected to the input sensor wire, key-on, engine-off, could run the coolant temp gauge sweep from 100F - 220", remove carefully, measure with a DMM, then compared to actual temp sensor both hot & cold. This could lead to burns if not careful, but short of installing a new gauge type sensor (Not idiot light switch) would be a cheap $9 venture from RockAuto. For my money, as stated before, using a plastic fork / door removal tool with a rag across the gauge face, you can pop off the needle and reposition as needed. (Good time to paint orange needle back to life)
Just the peace of mind while driving, looking ever so briefly at the temp, you like to see it straight up and down or middle...I would be happy.
