My montes been sitting for probably a year or so. I start it and let in run for 30 min or longer and take around block every couple months. I took it out a couple days ago, made it about 1/4 mile then it shut off. Wasnt really paying attention to gauges was going after my dog that got out. There wasnt any bells or whistles on start up with abnormal gauge readings. Got p0520 low oil pressure. Replaced oil pressure switch. No fix. Rang the wiring on the oil level sensor and pressure switch grounds and to pcm. 1 ohm all legs no grnd shorts or shorts together. Read 0v at oil pressure plug during start attempt, prob normal as its indication on off switch only. Tried 5a jumper on plug n start. No start. Read switch during start, no change on switch activation. Down to pcm, oil pump, or oil psi relief valve. Only have obd2 code scanner actron. Ordered oil psi regulating/releif valve, spring, and gasket. 25 bucks in parts. After that its either pcm, oil pump, or engine problem. Pcm and oil pump high cost. Pcm requires programming, cant do myself. Oil pump looks pretty involved to get to and take apart. Any advise? 2004 chevy monte carlo ss vin k 3800 series II.

 

More details. Reset/cleared p0520. Engine started and ran for 1 min before shutting off. Oil gauge on dash was 0, no change. One would think / hope the pcm reports data to the cluster seperate of engine operation.

 

I have almost the exact issue that just developed. Did you find anything out yet?

 

My 05 3.8L has been sitting for over a year, I start it every couple weeks or month and let it idle for a while. I have taken it around the block a few times but not farther than that. Acouple months ago it had a P0300 and P0303 misfire code, seemed to start fine but run a little rough. I was planning on pulling the plugs to check everything out. The next time i started it, the oil pressure gauge was not reading, i had previously replaced the stepper motors in the cluster so they were all working. The car just shut off and would only crank over. I did the enhanced obd2 and found a stored 0520 oil pressure circuit code. I changed the oil and replaced the oil pressure sensor and it still just cranks and will not start. I havent done much diagnosing yet.

 

Havent got around to it yet and was awaiting parts. Spoke to a mechanic i trust as well. Was trying to figure out cost and towing and who can do what. Gm wants 180 in labor for pcm. My mech can do the crank cam snsr relearn with his obd2 device but not vin programming. He was leaning towards fuel pump. The sw is just on off n it tells pcm to start fuel pump. He suggested listen for fuel pump kick on and check fuel psi wit a gauge. The gm fims say change switch, jumper, check wiring which i already did then says change pcm. My plan is to replace the oil pressure regulating valave in oil,filter housing, spring, and gasket. Test the switch using air pressure and meter. Hook oil,gauge to the oil sending unit switch port and look for 10-15 oil psi during start attempt. If no pressure prob oil pump or engines toast. If psi, reinstall oil sending switch if tests good. Check fuel psi @ the rail shrader. Order pcm from ebay programmed to vin. Do key relearn and hope will,start with probable crank code. If no fix prob tow it to my mech. He cant reprogram a cluster however n gm,claims they cant use a junkyard 1. Replaced cluster 10 yrs back n it was 500 bucks. It was speedometer then but car still drove just without indication. Hoping oil psi is same. Could prob test gauge with a dc power supply, prob.... Thats my plan. Was hoping for some advise on here for sure fire fix,but no luck.

 

I think this is spot on and a good place to start.

If the engine really is at zero oil pressure, youve got way bigger problems than the other possible things going on.

 

Finally got around to checking things out. Baterry is dead now, but nonetheless jumped it to my other car and tested. Got 60psi during attempted start. Prob means ind issue with system. Can anyone verify the voltage at the oil pressure switch just above the oil filter? Read somewhere online someone had 9.8 volts. Gm manuals dont really state anything about voltage. Think my pcm got shorted from power steering fluid spill that got down on the sensor.

 

Eh. This things being weird. Got 12vdc at connector. Tested switch on compressor, 2.2 ohm goes open with 5psi or higher.

 

P0520 summary. Replaced eng oil pressure sender unit. Checked wiring from sender unit to pcm and from pcm to splice block under dash. Checked good. Had 12vdc at oil sender unit plug. Tested oil sending unit using compressor. 2.2 ohm at 0psi, after 5-10psi or so goes to open/ol. Tested oil psi with a mechanical gauge. Had 60psi during start attempt. Cant for the life of me figure out what data the pcm uses to display the oil pressure. Manufacturer manuals state oil psi sending unit is open/close switch reports to pcm to control fuel pump. Pcm reports oil pressure data to instrument cluster. Been up and down all description and operations as well as all the wiring schematics and theres no info on where the pcm gets the data to display the variable oil pressure on the oil psi gauge on dash. Does anyone know what data the pcm uses and/or where it gets it from to generate the variable oil psi on the instrument cluster? Reaching point where i may have to tow it to repair station.

 

Have not made much progress on mine, still sitting. I did confirm i have 55psi oil pressure when cranking. I have a new BCM installed and did the learn procedure I found on this forum, it cranks but no start. Gonna go back and check basics and recheck it has spark and fuel, now that the new BCM is in.