2018 Expedition Intermittent Low Oil Pressure Warning

[KOMaynard]

I have a 2018 Expedition (85k miles) that has been showing a P0521 code, however, 99% of the time the gauge on the dash reads normal.

I replaced the oil pressure sensor and did an oil change, however, the error code returned a day or two later and has continued to intermittently show. Once in a while the dash will read “low oil pressure”, however, the gauge will return to normal with a moment and/or upon restart.

Per Ford Pass this is the error “The engine control system has detected an electrical signal from the engine oil pressure sensor that is outside of its normal operating range.”

I took everything back apart and cleaned both the sensors harness plug and the wire harness plug with CRC Electronics cleaner, and the issue has remained.

I also want to note I found a little bit of oil in the intake tubes that I had to remove to access the oil pressure switch. Nothing major, and I’m guessing it’s probably normal, but I will note it.

Since this issue has started, I also began receiving Ford Pass warnings indicating “An Electrical Short Turbocharger Wastegate Actuator Motor or Associated Circuit Wiring” and “low boost pressure with the turbocharger”. Which I will note, I have experienced no signs of engine or turbo issues. The only time the vehicle feels underpowered is when it clearly gets put in limp mode after an oil pressure warning.

I also received these warnings: “Your Service Engine Soon alert is on because there is an electrical issue with your vehicle. Your vehicle may be drivable, however Anti-lock brake operation and other important driver assistance features may not operate properly.” and “Your service engine soon (malfunction) alert is on because there is an electrical issue with your vehicle. This may cause additional warning alerts and other features in the vehicle to not work properly. Your vehicle is drivable but not all driver assist features are active.” and “Illuminates when the system has detected a powertrain or a four-wheel drive fault.”

Has anyone dealt with these or similar issues? I don’t believe I’m actually losing oil pressure, I believe it’s wiring or some other error, nor have I experienced any drive-ability issues.

I also have an active recall for the 24E13 campaign. Which I don’t believe is related - but perhaps if there’s a needed PCM reflash/reprogram?

 

[99WhiteC5Coupe]

I have a 2018 Expedition (85k miles) that has been showing a P0521 code, however, 99% of the time the gauge on the dash reads normal.

I replaced the oil pressure sensor and did an oil change, however, the error code returned a day or two later and has continued to intermittently show. Once in a while the dash will read “low oil pressure”, however, the gauge will return to normal with a moment and/or upon restart.

Per Ford Pass this is the error “The engine control system has detected an electrical signal from the engine oil pressure sensor that is outside of its normal operating range.”

I took everything back apart and cleaned both the sensors harness plug and the wire harness plug with CRC Electronics cleaner, and the issue has remained.

I also want to note I found a little bit of oil in the intake tubes that I had to remove to access the oil pressure switch. Nothing major, and I’m guessing it’s probably normal, but I will note it.

Since this issue has started, I also began receiving Ford Pass warnings indicating “An Electrical Short Turbocharger Wastegate Actuator Motor or Associated Circuit Wiring” and “low boost pressure with the turbocharger”. Which I will note, I have experienced no signs of engine or turbo issues. The only time the vehicle feels underpowered is when it clearly gets put in limp mode after an oil pressure warning.

I also received these warnings: “Your Service Engine Soon alert is on because there is an electrical issue with your vehicle. Your vehicle may be drivable, however Anti-lock brake operation and other important driver assistance features may not operate properly.” and “Your service engine soon (malfunction) alert is on because there is an electrical issue with your vehicle. This may cause additional warning alerts and other features in the vehicle to not work properly. Your vehicle is drivable but not all driver assist features are active.” and “Illuminates when the system has detected a powertrain or a four-wheel drive fault.”

Has anyone dealt with these or similar issues? I don’t believe I’m actually losing oil pressure, I believe it’s wiring or some other error, nor have I experienced any drive-ability issues.

I also have an active recall for the 24E13 campaign. Which I don’t believe is related - but perhaps if there’s a needed PCM reflash/reprogram?

Something basic: Did you change the oil and use the correct viscosity and an OEM Ford oil filter?

The other warnings may be a result of a weak or failing battery, and or loose or corroded battery terminal connectors (look under the red vinyl positive battery terminal cover).

 

[KOMaynard]

Yes, 5W-30 (Valvoline Full Synthetic Restore and Protect) and then not the Motorcraft Part, but the Mobil1 equivalent, M1-212A.

I’ll double check the positive terminal, but I had check both terminals when I put the negative back on after switching out the sensor.

 

[KOMaynard]

No corrosion on the battery terminals, metered at 12.18V. (Previously, per data pull yesterday, 14.73V while motor was running).

Oil level is also in the right range per dipstick.

I should also note, the Mobil1 filter is the same one I’ve used without incident for the last 5-6 oil changes since purchasing the vehicle. (Not ruling out a flawed unit for either the new filter or the new sensor for that matter.).

 

[05Superduty]

Do you have the capability to datalog your driving? Not overly familiar on these 3.5's as I just got my expy, but I'm wondering if your oil pressure is dropping during your drive? Maybe after a good pull and you come to a stop at a red light or something? Are you using Auto Stop/Start? Have you had any really wet weather before this started acting up? Just trying to throw idea's out and see what sticks to the wall.

 

[UnrulyBeardsman]

You mentioned you replaced your sensor, there could still be two issues one the aftermarket sensors off of Amazon are not the most reliable so could still have a bad sensor. Another possibility could be the actual clip plug could be deteriorated or even the wires corroded that can connect to the sensor.

Grab a new sensor and swap that out again and I’d also check the wires/clip.

 

[KOMaynard]

Do you have the capability to datalog your driving? Not overly familiar on these 3.5's as I just got my expy, but I'm wondering if your oil pressure is dropping during your drive? Maybe after a good pull and you come to a stop at a red light or something? Are you using Auto Stop/Start? Have you had any really wet weather before this started acting up? Just trying to throw idea's out and see what sticks to the wall.

I do, but my reader doesn’t have oil pressure. That was my initial thought. I have an innova code reader that ties to my phone via Bluetooth. I’ve been trying to avoid getting Forscan on top of that. It is awfully rare that I get the “low oil pressure” warning on the dash, I think over the past few weeks, it’s happened twice. Both of which the gauge immediately recovered, or recovered on restart. We haven’t had any wet weather.

There is some update to the vehicle.

So prior to Sunday night, I hadn’t noticed the issue, and had just assumed I had spilled some oil/had the funnel burp while filling on a previous oil change. But I have the common failure point on the driver side valve cover, kind of near the throttle body.

Additionally, last night a coolant leak presented itself with some wet spots under the truck at work. Looks like the leaks are on the passenger side of the truck, with some coolant leaking on the passenger side frame in the FR wheel well.

My now running theory, unconfirmed of course, is that the coolant leak or the oil leak has caused some shorting on that main PCM harness that holds the Oil Pressure Sensor, and the aforementioned turbo sensors. I’m working to get some diagrams so I can try and track back the harness to rule it out or confirm. I’m really hoping I won’t have to replace the harness at roughly $470, but we’ll see.

I haven’t determined the source of the coolant leak, but I’m assuming one of the metal crimps on one of the coolant hoses split and that’s my source. I didn’t have a chance to really troubleshoot that since finding it.

 

[KOMaynard]

You mentioned you replaced your sensor, there could still be two issues one the aftermarket sensors off of Amazon are not the most reliable so could still have a bad sensor. Another possibility could be the actual clip plug could be deteriorated or even the wires corroded that can connect to the sensor.

Grab a new sensor and swap that out again and I’d also check the wires/clip.

The new sensor is aftermarket, however, I grabbed it from O’Reilly’s. It was a Standard Motor Products option. Which I believe are fairly reliable aftermarket options. The idea has popped into my head, however, it reads oil pressure constantly on the gauge.

The wires and clip were oil logged when I changed it initially, and have since been cleaned and reconnected. There was no visible corrosion on the plug or wire though. However, the wire could be potentially compromised with oil; especially with the valve cover issues I just found. OR the coolant issue that’s also presented could be the culprit on the other end of the wiring.

 

[BMW2FORD]

Can you un screw the sender and install a mechanical gauge to check oil pressure? That would rule out a mechanical versus an electrical problem. The Gen 2 Ecoboost engines do have a variable oil pump. Below 1400 the pump is in low flow / low pressure mode to save drag and fuel. There’s a wiring connector on the pass side lower timing cover that faces forward which has a solenoid in the oil pump that connector connects to in the oil pump that controls this system.

 

[KOMaynard]

Can you un screw the sender and install a mechanical gauge to check oil pressure? That would rule out a mechanical versus an electrical problem. The Gen 2 Ecoboost engines do have a variable oil pump. Below 1400 the pump is in low flow / low pressure mode to save drag and fuel. There’s a wiring connector on the pass side lower timing cover that faces forward which has a solenoid in the oil pump that connector connects to in the oil pump that controls this system.

I have an appointment to have this diagnosed next week. I’m gonna try and avoid it if I can.

Last night, there was a small update to this. The coolant leak was coming from the Heater Hoses. I ended up replacing both, one was definitely leaking, the other had splits in the metal crimps, so I didn’t wanna take any chances. I had been having some cooling issues leading up to the more noticeable leak (very minor, essentially when stationary, the truck would tick up into the 230s and 240s, where the dash reads a number, but never crazy hot). So I wonder how long it had been leaking, and if that plays a role in all of this.

Additionally, I don’t know if it’s related to any of this, but I found a little oil leaking around and on the rubber seals the passenger side VVT solenoids.

 

[KOMaynard]

Further update: I have been able to find a definitive way to trigger the low oil pressure light/warning. It immediately will alarm the second my car performs an auto start/stop.

For example, I have found that if I pull up to a red light, and the vehicle goes into auto start/stop, shutting the engine down, once the vehicle sensor updates to show that there's no oil pressure on the dash (because the motor is off) and the vehicle kicks on when I release the brake pedal, the dash will continue to read no oil pressure and after a few seconds throw the "Low Oil Pressure Warning". I haven't had this be an issue on a normal start, even when performing several in a row.

I have the troubleshoot scheduled for the morning but am debating performing a battery change to rule out the earlier suggestion, before it goes in. I will note, that since changing the heater hoses, I haven't received any warnings for the turbos. The passenger side turbo was taking quite a soaking from that leak, and I'm thinking that was the root cause of those lights.

 

[KOMaynard]

Problem solved.

I did replace the battery, however, that was not a cause. When it was diagnosed, they found that the Oil Pressure Sensor was reading 140 PSI with the engine off. Turns out, my replacement sensor was either faulty from the factory OR incompatible with the Expeditions computer system. (UNRULYBEARDSMAN called it). This also has made a strong case for me to buy FORSCAN, to open self-troubleshooting doors.

I have since replaced the sensor with a factory Motorcraft part and the issue is completely resolved. Rule of the story: Buy the Motorcraft Part if its anything electrical to avoid a headache.

I will still have to get the driver side valve cover replaced, which I'm torn on having it done, or, trying to take it on myself. That's a whole different issue. The coolant leak was definitely the root cause of the turbo errors, as those have also disappeared completely since the heater hose replacement.

Hopefully this helps someone if they run into a similar issue. Thanks all for the help.

 

[Mr Big]

Problem solved.

I did replace the battery, however, that was not a cause. When it was diagnosed, they found that the Oil Pressure Sensor was reading 140 PSI with the engine off. Turns out, my replacement sensor was either faulty from the factory OR incompatible with the Expeditions computer system. (UNRULYBEARDSMAN called it). This also has made a strong case for me to buy FORSCAN, to open self-troubleshooting doors.

I have since replaced the sensor with a factory Motorcraft part and the issue is completely resolved. Rule of the story: Buy the Motorcraft Part if its anything electrical to avoid a headache.

I will still have to get the driver side valve cover replaced, which I'm torn on having it done, or, trying to take it on myself. That's a whole different issue. The coolant leak was definitely the root cause of the turbo errors, as those have also disappeared completely since the heater hose replacement.

Hopefully this helps someone if they run into a similar issue. Thanks all for the help.

Glad you found the issue. And CUDOS to @UnrulyBeardsman for the good call.
Great advice about purchasing Genuine parts. I've had my share of issues buying after-market to save a little money. In the end it really saves nothing and causes a whole lot of grief.