Gauge says low oil pressure

2016 5.7 flex Crewcab, 104K miles.
The oil pressure is normally just a bit below the center of the gauge. Today I am driving and see that it's almost at the very bottom. When I shut off the engine, it drops a bit more. When I restart the motor it comes up a bit but only to a level that is way too low, just barely above nothing. Engine sounds and drives normally.
Checked the oil level it's fine. No dash lights are on when driving. (check engine, oil light, etc)
I assume it's an electrical issue. But need advice on how to diagnose that.

Is this an issue that any of you have experience with?

Thanks.

 

It could be oil pressure sending unit, bad oil pump, etc. I would swap out sending unit-not too expensive.

 

Well, new sensor reads the same thing. I could not find a manual pressure gauge that would fit.

I would think that if I really had no oil pressure that the engine would be clacking like crazy. Anyone with an opinion on that?

There are no warning lights or messages at all on the dash. If the computer saw no oil pressure, wouldn't there be some sort of alarm going off?

 

You need to hook up manual gauge to confirm pressure is low.

 

First thing I would check is the oil filter, make sure it still has the metal tube inside it and isn't collapsed. Easy and rules out a failure point seen here before.

An engine may not clatter right away when low on pressure. I was riding in my friend's Avalon when he ran it just about out of oil. The light kept popping on and off until we got it off the road and it still sounded as smooth as ever. Thankfully the motor survived that one without issue.

 

Checked the oil filter, all OK there.

The truck has been driving fine this whole time, so I am confident that the truck has oil pressure. Both old and new sending units are working and they do show oil pressure when the truck is running (I checked resistance with a multimeter while on the truck with the engine off and running.)

Still no codes of any kind, not sure there would be any though. The wiring diagram shows the sensor going to the instrument cluster directly and even running the engine with the sensor unplugged doesn't cause any codes. Surely it takes a reading somewhere for oil pressure, maybe in the variable valve timing circuit (?).

I got a month subscription to alldata. I need to test the resistance in the circuit from the sender to the back of the cluster. If that's OK then I guess I need to repair or get a new instrument cluster.

 

Have tried a obd reader that you can read the oil pressure on?

 

Does the gauge move up when you floor it? Maybe the needle is stuck or can’t go higher. Mine moves a little when I give it gas then drops back down.

 

What were the resistance values of the sensor when the engine was off vs when it was running and should show normal oil pressure?

The cluster should just read the resistance value from the sender, factor in the RPM signal and this powers the gauge.

On other thought its to unhook the battery or unplug the cluster from the harness to let all the power drain out and reset it. Maybe the programming in your cluster glitched out. Worth trying I would think.

 

The resistance on the sender with the truck running was 35.2 ohms, I think. Regardless, if I actually had no oil pressure I am pretty sure the engine would have seized up by now. I will check the circuit between the sender and the cluster to make sure it's not an open circuit and that it's not grounded along the way. If that is all good, then I probably need a new cluster. Maybe I can send mine off to a repair place, if there is such a thing for Toyota clusters.

The gauge does not move at all with engine RPM. I have not tried an OBD reader to see if i can find an oil pressure number.

 

Manual gauge. Stop relying on the electric. And you can have insanely low oil pressure and still have the engine run.

 

Spraynard agrees. Pressure is analogous to volume although it is an assumption. Low pressure can result in the components furthest from the pump starving. Personally, if I had to guess, i would say that the piston rings would be the most starved since they rely on a spray; not a splash.

 

Mystery solved. Mouse chewed a wire.

 

I think I have the same problem. Big Ed, where did you find the chewed wire?

 

Also have that question. Manual gauge check is always the best if possible.

 

@Big_Ed