Oil pressure and engines 101...
Anytime you have an oil indicator light come on while the engine is running, you should immediately shut down and check oil pressure with a mechanical oil pressure gauge.
One of two possibilities can exist:
1) the idiot light/warning indicator is false and the oil pressure is fine
2) the idiot light/warning indicator is accurate and you don't have oil pressure.
You have to ask yourself "do you feel lucky today?"
Number 1 is a cheap fix, number 2 will be expensive as in engine replacement or rebuild.
If we make a bad call on a semi engine and it seizes, we are looking at about $25,000 - $35,000 repair. So we don't guess, we check. It hasn't cost us money turning it off!
Once you establish that you do in fact have the correct oil pressure you can properly diagnose the issue. One thing that may be happening is the pcm thinks the engine doesn't have oil pressure and will cut back all performance to try and by some time before it seizes.
