Help us help you. By posting the year, make, model and engine near the beginning of your help request, followed by the symptoms (no start, high idle, misfire etc.) Along with any prevalent Diagnostic Trouble Codes, aka DTCs, other forum members will be able to help you get to a solution more quickly and easily!
Engine oil pressure switch code p0521 i checked the sensor looked new even checked the filter brand new so before i assumed a faulty sensor i checked 5v ref checked the low ref aka ground side no issues there..even checked for any voltge drop nothing but when i check the signal wire full battery pack voltage mind you the signal wire does not share with any other sensors it just directly goes to the ecm according to pro demand could it be a short? also i ran across another issues where i disconnected one of the connectors from the ecm and plug it back in carefully because i was testing voltage there and now i have like 12 codes out of no where which it did not have before could it be i short circuited the ecm by unplugging it and plugging it back in with the key on? car has trouble starting... like crank sensor codes showed upeven low air volume codes popped up for no reason if it wasnt even there to begin with?
Generally when I come across a P0521, it is pretty straight forward. Hook up a scan tool, looking at the oil pressure pid. Unplug the sensor, should be 129psi (somewhere around there). Jump 5v ref to signal wire. Pid should say 0psi. I might have it backwards but that is normally what I do.
I'd advise. Don't unplug the PCM with the key on anymore. How are you testing your wires? It is not recommended to check 5v circuits with a test light. Correct terminal adapters should be used for testing and/or jumping. You need to be careful not to spread the terminals. They are small and do not take much to spread to wide.
Clear all the codes and/or disconnect you negative for 1 minute and start diagnostics over. If you have 12 volts on you EOP sensor signal wire with it unplugged, then I would suspect there is a short to voltage in your engine harness. There should never be 12 volts on any of the wires for the EOP sensor. Hope this helps some.
