2003 Tahoe LS, 196,000 miles, 4.8L V8 Vortec.
My Tahoe went into reduced engine power mode more than 10 times in a row as I was driving on a two-lane highway, traveling around 50-55 mph. I kept clearing the code and it kept coding. Throttle body/throttle position sensor was replaced at 193,000 miles. TAC module was replaced at 174,000 miles. Grounds have been checked. Any suggestions or advice?

 

Had the same code come up in my 22 Silverado on a cold start, turned out the TP sensor was toast, replaced it and the code went away, so definitely worth checking that out first.

 

Yeah, I've ran into that code before on my 2022 Silverado, P1514 is usually related to the camshaft position sensor, so I'd recommend cleaning or replacing it to see if that clears the code. Make sure to check the wiring too, I've seen some weird issues with corroded connectors causing this error.

 

P1514 is related to the EGR system, so check your EGR cooler for coolant leaks or blockages, that's where I'd start. And make sure the EGR valve itself isn't stuck open or closed, that's a common cause of this code popping up.

 

I had a similar issue with my '22 Silverado 1500, got the P1514 code due to the fuel system performance monitor. Check the fuel injectors and the fuel pressure sensor, you might need to replace one or both to sort it out. Also, make sure your fuel tank is at least 1/4 full, some guys suggested it was causing random issues.