I'm working on a 2012 Maxxforce 7 that sets fault SPN 100 FMI 18 "Engine Oil System Below Warning Pressure". This one has us stumped. According to the service manual the criteria for setting the fault is when the oil pressure drops below 12 psi at certain RPM's and for a certain amount of time. The oil pressure reading through Navistar Engine Diagnostic software is 60 psi and at the diagnostic port with a pressure gauge we are getting 80 psi when the fault becomes active. We have tried swapping ECM's with matching trucks, installed a known good pressure sensor and have also had the ECM updated to the most current software. We have ohm'd out all the wiring related to the pressure sensor and have also put a new plug/pigtail on for the pressure sensor. Any thoughts? Is it possible this fault is only related to the engine protection system and it has the incorrect pressure programmed into it? The oil pressure never drops to the critical level at any RPM or temperature. Thank you in advance.
When you say "ohm'd out" did you load test it and check the voltage drop or just meter it out on the ohms scale? one good strand of wire will still give you a good reading in ohms. could be a short to another circuit in the harness. service info for that code states :Fault Overview Fault sets when the Engine Control Module (ECM) detects Engine Oil Pressure (EOP) lower than expected for current oil temperature and engine speed is the oil temp sensor reading correctly? Does the pressure, temp and rpm match the threshold chart they list in the diag info? also :Oil pressure at filter module diagnostic port will also be 20-30% higher than reading at Engine Oil Pressure (EOP) sensor port. Therefore ServiceMaxx™ oil pressure reading will be lower than manual reading taken at diagnostic port.