Is thr a switch that lets the nito know that u had changed the oil

that is the light to let you know there is no oil pressure (in theory). If the engine is not making any unusual noises than its probably just a bad oil pressure switch. The switch it typically located near the oil filter. usually a 1 1/16 oil pressure socket is needed to remove and replace the switch.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

The "Oil Change Reminder Light" has to be reset.

To reset the oil change reminder light with the accelerator pedal, turn the ignition switch to the ON position. Do not start engine. After turning the ignition ON, depress the accelerator pedal fully to the floor and let it up again 3 times within 5 seconds. The oil change reminder light should flash a few times to let you know that it is resetting. If it does not flash, turn the switch OFF and repeat the procedure. After it flashes, turn the ignition switch OFF. Then start the engine. The light should come on for a bulb check then go out and stay out.

For Buick Le Sabre, 1995-99, when "CHANGE OIL SOON" light is on:

• Access the reset button in the glove box (refer to car manual if required).
• With the engine off, set the ignition switch to the RUN position
• Press and hold the reset button in the glove box for at least 5 seconds
  
• The light should blink a few times (4) then go out!

Hope it helps: let me know how you go.

all car well have a oil pressure sensor, the oil pressure sensor is what lets you know, you have good oil pressure, if light comes on low oil pressure, need to turn off engine before major engine damage occurs, the oil pressure switch will be next to the oil filter, screw into the engine block, your car also has a oil pan sensor, called oil level sensor, that one screw into the side of the oil pan, it let you know when your some what low on oil.

DID YOU TURN ON IGNITION SWITCH ON AND SLOWLY DEPRESS AND RELEASE THE ACCELERATOR PEDAL 3 TIMES WITHIN 5 SECONDS.IT WILL TAKE LONGER TO RESET DETERMINE HOW LONG YOU LET THE OIL LIGHT STAY ON.WHEN YOU TURN ON SWITCH 5 SECONDS DEPRESS AND AND RELEASE ACCELERATOR 3 TIMES.IF DONT RESET.TURN OFF SWITCH.THEN TURN BACK ON.YOU MAY HAVE TO DO IT SEVERAL TIMES.LET SWITCH REST SOME TRY AGAIN.IT WILL TAKE A WHILE.WHEN EVER CHANGE OIL SOON LIGHT COME ON RESET IT THEN AND CHANGE OIL.DRIVE IT ON A WEEK OR TWO TAKES LONGER TO RESET.

seems like your oil pressure switch gave up, its located on the side of the oil filter, you can take it out and test with a amp meter. it should cost you less than 20 bucks to buy something like that.

With the ignition switch on but the vehicle not started simply press the gas pedal all the way to the floor 3 times. This action will reset the OIL light. This is a orange display on the dashboard that will light up once and reset. Let me know how this works for you!

some of these cars had a low pressure fuel cut off switch buit into the oil pressure switch, make sure you have the correct oil sending unit. hope this helps let me know. ps use a a/cdelco part

Press and hold the SELECT/RESET
control switch to select SYSTEM
CHECK when “SYSTEM CHECK /
HOLD RESET” is displayed in the
message center. Selecting this
function from the SETUP MENU
causes the message center to cycle through each of the systems being
monitored. For each of the monitored systems, the message center will
indicate either an OK message or a warning message for two seconds.
Pressing the SELECT/RESET control switch cycles the message center
through each of the systems being monitored.

The sequence of the system check report and how it appears in the
message center is as follows:
1. OIL LIFE RESET
2. CHARGING SYSTEM
3. WASHER FLUID
4. DOOR AJAR
5. EXTERIOR LAMP
6. BRAKE SYSTEM
7. PARK BRAKE
8. MILES TO EMPTY
9. FUEL LEVEL LOW (will only display if 50 miles or less to empty)
To reset the oil monitoring system to 100% after each oil change
[approximately 5,000 miles (8,000 km) or 180 days] perform the
following:
1. Enter SYSTEM CHECK to display
“OIL XXX% RESET IF NEW”.
2. Press SELECT/RESET control
switch to display “HOLD RESET IF
NEW OIL”.
3. Press and hold the
SELECT/RESET control switch for
more than 2 seconds. Oil life is set
to 100% and “OIL CHANGE SET TO
100%” is displayed.

the pressure sender is near/next to the oil filter. And yes this does sound like a sender issue.