I have a 2005 GMC Sierra 1500 SLT Extended Cab with a 5.3 litre engine. I purchased the truck a few months ago with 230,000 KM on it. I have had oil pressure issues with the oil pressure gauge providing erratic readings and even sounding the warning bell when the pressure fell below 10 psi. In response, I have recently replaced the oil pressure sensor with limited success in eliminating the problem. When the engine is below operating temp the pressure gauge will still show pressures below 10 psi during idle. If I increase the rpm, the pressure will come back up to a more normal pressure. I have read posts that the oil pick up tube that feeds the oil pump may not be seated properly and the “O” ring may be faulty. Does anyone else have a suggesting as to what my next step should be in order to repair the oil pressure issue?
I suspect the previous owner sold the truck for this exact reason. If you did an oil change after you bought it, you put in the correct weight oil. The previous owner maybe filled it with 15W50 oil to make the oil light stay off. If that is the case, you may need a new engine.
To find out for sure, temporarily install a real, mechanical pressure gauge into the oil sender port. Check the pressure and make sure you aren’t chasing your tail looking for a mechanical problem where an electrical one exists.
If the truck’s gauge is shown to be accurate, if you want to save the engine, drop the oil pan. That will allow you to check the pickup O-ring and the screen. If it looks OK, it probably is. The pan off allows you access to the rod bearings. I’d suspect one or all are worn. If you are lucky, those will be worn and you caught them before they damaged the crank pins so new shells ca be installed. I’d check the main bearings, too. This will be a pain. Good Luck