While the 5.9 Cummins is one of the best and most sought-after diesel engines ever made, it still has its shortcomings – especially the oil pressure sensor.
The oil pressure sensors are known to go bad on these engines and show erratic readings, or just show zero oil pressure at times, even though the engine seems to run fine. Combine that with a whacky factory oil pressure gauge by Dodge, which doesn’t even monitor the actual oil pressure and just serves the driver an estimation, and you get a lot of confusion among owners.
So if your truck’s oil pressure gauge is acting up, and you’re suspecting a bad oil pressure sensor, then you’ve stumbled to the right place. In this article, we’ll discuss the 5.9 Cummins oil pressure sensor location, how to diagnose the sensor, and how to replace it.
12v & 24v 5.9 Cummins Oil Pressure Sensor Location
The oil sending unit (oil pressure sensor) on the 12v 5.9 Cummins is located on the driver’s side of the engine, below the bottom right side of the injection pump, and next to the power steering reservoir.
On the 24v 5.9 Cummins, the oil pressure sending unit is located on the same driver’s side of the engine but has been moved below the ECU (that shiny steel box).
How to Diagnose a Bad 5.9 Cummins Oil Pressure Sensor
If the oil pressure sensor on your 5.9 Cummins is showing erratic readings and low/high oil pressure, then 9 times out of 10 the problem is a bad oil pressure sending unit. With that said, there could be a wiring issue in the sensor circuit, or your 5.9 could actually be having serious mechanical problems (those are rare).
The best way to diagnose a bad oil pressure sending unit is by installing an aftermarket mechanical oil pressure gauge and monitoring the actual oil pressure. Luckily, there is a 1/8×27 MTP oil pressure test port right on top of the oil filter housing, which can be used to connect a mechanical oil pressure gauge.
With the mechanical oil pressure gauge installed, you can monitor the actual oil pressure of your 5.9 Cummins. The 03-07 Dodge oil pressure gauge in the instrument cluster is not a real oil pressure gauge and should not be trusted, more on that in this article – Normal 5.9 Cummins Oil Pressure at Idle?
Your aftermarket mechanical oil pressure gauge should show around 20 PSI at idle and around 50-65 PSI at 2000 RPM if your engine is strong and healthy. If the readings on your 5.9 Cummins are similar, then you do not have a mechanical problem inside the engine, and the culprit is the oil pressure sender unit or its electrical circuit.
How to Replace 5.9 Cummins Oil Pressure Sensor
Tools you that will need: a long (3”) thin-walled six point 1 1/16” socket or a long 27mm socket, two wobble extensions, ratchet, small flathead screwdriver, or a pick for the connector.
Step 1: Disconnect the oil pressure sensor
Lift the tab on the connector with your fingers and pull/wiggle the connector apart. If the tab is difficult to move, then try using a small screwdriver or a pick to pry it up. Be careful not to break it.
Step 2: Remove the wheel trim
The pressure sensor can be accessed through the wheel well on both 24v and 12v 5.9 Cummins generations. It can also be done from the engine bay if you have long hands and fingers.
Step 3: Unscrew the oil pressure sensor through the wheel well
You will need two extensions to reach the sensor.
Step 4: Screw in the new oil pressure sensor
Keep in mind that the sensor is not a bolt, so don’t overtighten it. Just a bit more than hand tight should be enough.
Step 5: Reconnect the oil pressure sensor connector
Eddie is the co-founder of CarCareCamp.com, and the site’s primary contributor.
Under his belt, Eddie has a bachelor’s degree in Automotive Electronics Engineering and almost a decade of experience working as a semi-truck technician (specializing in electrics).