Can you bypass the oil pressure sensor?

A930Rocket · 01:10 PM

Friday, I installed a mechanical oil pressure sensor with digital gauge in my 2014 F150, in addition to the stock sensor. I did this, because I was getting a low oil pressure warning on the dash and it would shut the engine down. I’ve done all of the usual suspects to fix the problem, including a new sensor, filter, oil, PCV, clean the throttle body, etc. but it happened again, Thursday.

After doing this, I wondered if I could fool the computer(?) by grounding (or ?) the stock sensor wire and just use my new mechanical gauge*.

The stock sensor/gauge is an on off switch. It tells you if you have pressure or not but not what it is.

What do you think?

* I know it’s there to protect the engine, but millions of cars have driven billions of miles with real oil pressure gauges, like I have now.

Arizona_928 · 07-26-2025, 05:16 PM

Add a resistor to the circuit. Question would be, which way to go…

Zeke · 07-26-2025, 05:58 PM

If he replaced the sending unit then the fault may be elsewhere. I'd Ohm both units first to see if they are normally open or closed. Then I'd reinstall to see what they read both electrically and with the harness off, how they Ohm when the digital is indication sufficient OP. It might be just grounding the hot by pig tailing or isolating the hot while grounding the 2nd wire. I'd be surprised that an OPS would be a resistance type unit. An oscilloscope would be handy to watch it in real time. I'm sure the ECM cares only about the B+.

But what I know about 2014 Fords is on par with my neurosurgery acumen.

A930Rocket · 07-26-2025, 06:03 PM

Electrical work is not my forte, but I have my old oil pressure sensor and I could Ohm that to see if it’s open or closed. My understanding is, the oil pressure either opens or closes the circuit.

I thought about just grounding the wire to the factory oil pressure sending unit to see what happens….

RANDY P · RANDY P's Garage

Pull the ****er out, stick a paperclip in the plug and start it.

See what it does.

A930Rocket · 12:58 PM

It only has one wire.

From a google search:

Here's a more detailed breakdown:
Function:
The sensor's main job is to detect low oil pressure, not to provide a precise reading of the pressure.

Mechanism:
It typically uses a spring-loaded diaphragm and a switch. When oil pressure is sufficient, it pushes the diaphragm against the switch, keeping it open and the warning light off.

Low Pressure Scenario:
If the oil pressure drops below a certain threshold (the "switch point"), the diaphragm relaxes, allowing the switch to close and the warning light to illuminate.

From the last paragraph, it would seem that the wire makes a connection to ground, sends a signal to the ECM for low oil pressure warning, and turns off the engine

masraum · 07-26-2025, 07:50 PM

So you have good oil pressure with the gauge. Butt I think the big problem pops up when the car has been driven fort several hours, right?
Have you driven far enough to test it yet?
How easy is it to unplug? Could you leave it plugged in and then just unplug it if you have a problem?

If it's a pain to unplug, then sure, just unplug it. I suppose it's possible that the ECU might look for the initial closed circuit but that seems unlikely.

greglepore · 07-27-2025, 04:03 AM

Do you have a warning light with the gauge? If not, I'd fool the ecu at the harness but also wire a light to the sensor.
If its actually activated by ground, I have to wonder if you have a wire rub in the harness somewhere.

Dixie · Dixie's Garage

Would you kindly share what the pressure gauge reads right before the light comes on?

A930Rocket · 10:24 AM

Mas, it’s super easy to unplug to test it, but I haven’t had a chance to either drive it or unplug it. Hopefully this afternoon. When I go back to work tomorrow, I’ll be driving my two hour commute and we’ll see what happens. And that said, it doesn’t happen every day, it’s random.

Greg, With the stock system, I get a low oil pressure warning on the dash and it immediately shuts off the engine. For me, this only happens at idle, but it’s happened to people driving on the highway. There is no warning. The message comes on and the engine shuts down.

Dixie, the gauge on the dashboard is a dummy gauge. It only tells you whether you have pressure or not, it does not give you accurate readings.

Edit: the stock idle is 600 RPMs. I might buy a tuner that raises the RPMs, to keep pressure up and can correct or calibrate the tire/MPH, as I’ve got bigger tires than stock. I’m not looking for one that will change the engine or transmission parameters

greglepore · 07-27-2025, 10:50 AM

Understood that part. My question more or less is whether if you disable the stock sensor whether you'd have a big warning without having to have eyes on the gauge. Not that you'd need anything that large, but I ran a big red autopower beacon on my dashtop in the hillclimb car to warn of low pressure. My only thought is that a few seconds of zero pressure is possible in a gauge only setup.

Zeke · 07-27-2025, 11:28 AM

Quote:

Originally Posted by masraum

So you have good oil pressure with the gauge. Butt I think the big problem pops up when the car has been driven fort several hours, right?
Have you driven far enough to test it yet?
How easy is it to unplug? Could you leave it plugged in and then just unplug it if you have a problem?

If it's a pain to unplug, then sure, just unplug it. I suppose it's possible that the ECU might look for the initial closed circuit but that seems unlikely.

That's actually a good thought because it might and if it didn't see the closed position when the key if is turned to on before start, it may trigger a code that if persistent could create a CEL. That would code out as a problem with oil pressure.

Once again, speculating only, However it seems to me that engineers look for ways to keep us from bypassing systems problems so as to keep the service bays busy. Not beyond reason.

masraum · 07-27-2025, 11:56 AM

Quote:

Originally Posted by Zeke

That's actually a good thought because it might and if it didn't see the closed position when the key if is turned to on before start, it may trigger a code that if persistent could create a CEL. That would code out as a problem with oil pressure.

Once again, speculating only, However it seems to me that engineers look for ways to keep us from bypassing systems problems so as to keep the service bays busy. Not beyond reason.

that was my thought.

A930Rocket · 05:00 PM

Quote:

Originally Posted by greglepore

Understood that part. My question more or less is whether if you disable the stock sensor whether you'd have a big warning without having to have eyes on the gauge. Not that you'd need anything that large, but I ran a big red autopower beacon on my dashtop in the hillclimb car to warn of low pressure. My only thought is that a few seconds of zero pressure is possible in a gauge only setup.

Without the stock gauge/set up, I won’t have the warning light on the dashboard I think. That said, I’m always looking up for traffic and don’t see the small oil pressure gauge at the top left of the instrument cluster

What I would like to do is something you did and that’s a warning light, higher up that grabs my attention

Dixie · Dixie's Garage

Quote:

Originally Posted by A930Rocket

Dixie, the gauge on the dashboard is a dummy gauge. It only tells you whether you have pressure or not, it does not give you accurate readings.

Gotcha, somehow I thought the gauge on the a-pillar was an aftermarket pressure gauge you'd hooked up.

A930Rocket · 07-27-2025, 12:56 PM

Quote:

Originally Posted by Dixie

Gotcha, somehow I thought the gauge on the a-pillar was an aftermarket pressure gauge you'd hooked up.

The gauge on the A pillar is an aftermarket, but I haven’t driven the truck yet, where the warning light has come on. Stay tuned!

A930Rocket · 09:23 AM

Update: it’s 100* and I drove just over two hours and 100 miles. At 60 mph and 1500 rpm, oil pressure is 30 psi. At idle, with AC on, in gear with foot on brake, it bounces between 11-15 psi.

1990C4S · 09:39 AM

At 11-15 psi, you are very low...I think the factory switch is about 7 psi? I am just speculating, but I think you probably had legit failures.

Forget the bypass, drive it and see what the gauge says when you get your next failure. The factory sensor is probably open at zero psi, and then pulls that single wire to ground when pressure is achieved. With the engine off measure the resistance of the switch to ground, it will likely be 'infinite'. If that's the case, ground the wire.

You might need to fool the ECU via a latched relay connected to the starter wire, then powered off when the key is off. But I doubt it...

I see some 0W40 in your future.

A930Rocket · 07-28-2025, 12:58 PM

0W40? Isn’t that thinner than the 10W30 I have in there now?

I haven’t had a chance to look into it, but what would normal oil pressure at idle and driving be?

If my oil pressure is low, how do I determine whether my engine is just worn out or it’s the oil pump? Unfortunately, on this motor, the oil pump is not accessible from the oil pan. It’s behind the timing chains and cover. Ugh.

1990C4S · 07-28-2025, 01:15 PM

40>30. You may need 20W50...but that's all early speculation.

You should have 15psi per 1,000 rpm as a rule of thumb. You had 30 psi at 1,500 rpm, that seems 'fine'. Seeing 11 at idle would worry me, 15 is 'okay'.

What is the highest you see accelerating with cold oil?

And don't forget, there's a 99% chance that your aftermarket gauge is damped, and will hide dips off throttle. It smooths out the data that it displays...