2002 Trailblazer. My oil pressure low dsiplay came on after driving 40 miles, the engine shut down. The oil was changed 1000 miles ago, oil level is fine. What could this be?

Sounds like the engine oil level is low.
Have you checked to see if it is full ?

Replace the oil sending unit. On top of the engine, in the center by the fire wall.

Are you idling or is it doing 10 PSI driving it? If it has many miles on it it could be just getting worn out and that would be low oil pressure at idle when hot.

Safety feature.Check oil, if low then fill then see if it will start.Always check oil level once a week if car burns oil a lot..

Fist check oil level, the sensor is a pressure switch worked by oil pressure, hopefully the sensor has gone faulty. The oil pressure needs checking, if the oil pump or relief valve has gone faulty, the engine is being starved of lubrication and is causing internal damage. It is advisable NOT to run the engine till the pressure has been checked. (hope it's the sensor)

No if the oil light has flickered you have oil pressure loss some time just belive the sensor do help us out. lifter do not cause oil pressure loss pressure is built in the rotation of the crankshaft. The knock under the plenum will point you to that cylinder that is affected, (main bearing) as for a 1995 the injectors can only cause a misfire but no knocking noise,will they honor the warranty

Did he check the oil? Is it low. It could have a big leak.

Your oil light indicates a low level of oil in the engine.
Check the level and fill it.
Running the car with low oil can destroy the engine.
Take it back to where you had the oil changed and tell them. then plug oil pug may not be seated or the filter may not be seated.

Hello. Those oil pressure readings are completely normal for you vehicle. Actually, in a vehicle with that amount of miles, those readings are quite good. It's normal for the oil pressure to rise and fall with engine speed. Keep doing those regular oil changes and you should get many more miles out of that engine.

get oil pressure test done and check for codes in PCM