Truly I don’t heard any ticking or knocking, the engine runs fine and got power; The GMC advisor told me that the oil filter lifter valve was clogged, and just need to be clean. Apparently they did that, but as far as I understand (what he said) to do that the oil pressure sending unit needs to be remove and they check for oil pressure and it was fine. The gauge does not do it all the time just sporadically (dropping the oil pressure in the gauge) , what I don’t get is that if they have to remove the oil pressure sensor to clean what they call “valve lifter” because was clogged why don’t replace the sensor?
I really appreciate your technical documentation; well I have not experience working on GM products; I am Automotive Engineer and work only in European market vehicles; converting them to meet the EPA and DOT USA regulations. (Most of my work is wiring and programming). But it makes sense what you say, when I get the car back yesterday it does not show evidences (manifold) of being removed, I don’t know how they check for oil pressure!!! Seems like the $$$ they charged me was just a taken to the cleaner. The replacement of the sensor is something that for sure I can do. (If was able to swapped the engine and transmission in my wife Honda odyssey I can do this too) THANKS YOU VERY MUCH YOUR HELP IS VERY MUCH APPRECIATED…
Circuit Description The engine oil pressure (EOP) sensor changes resistance based on engine oil pressure. The engine control module (ECM) monitors the signal circuit of the EOP sensor. When the oil pressure is high, the sensor resistance is high, and the ECM senses a high signal voltage. When the oil pressure is low, the sensor resistance is low, and the ECM senses a low signal voltage. The ECM sends the engine oil pressure information to the instrument panel cluster (IPC) via the class 2 serial data circuit.
Circuit/System Testing Ignition ON, engine ON, verify the scan tool Engine Oil Pressure Sensor parameter is within 0.7 V-2.8 V . If not within the range of 0.7 V-2.8 V , replace the EOP sensor.
Glad I could be of some help, and at least got you going in the right direction! Have a great day!