JKU07

2007 JK Unlimited, 3.8L,

Oil Pressure light has been coming on intermittently. I've checked the obvious items of correct oil amount, viscosity, and oil filter replacement. I also replaced the Oil Sending Unit, and inspected the wiring. No codes are stored.

Oil pressure light still comes up intermittently, so I had the dealer tape an Oil pressure gauge to the windshield and drive it.

Oil PSI at idle was 15
Oil pSI driving was 35-70 psi

The engine appears to have the correct pressure, as The low pressure switch activates when oil Psi drops below 4psi. I took it back from the dealer who offered no explanation, other than the usual "wiring gremlin".

I've been driving it for a weak or so with intermittent OIL dash light, and non-stop dinger indication. Im seriously close to removing the audio dinger since I have no verified that the correct oil pressure exists.

Any help would be much appreciated.

jtphoto JK

Sounds like I short in the wiring which can be very costly to find. If you unplug the oil pressure sensor and drive it what happens?

So, for piece of mind you could permanently instal a oil pressure gauge.
All I can add is that you trace the wiring from the sending unit back to see if you find a bad spot.

Long shot... Run an auxiliary 4gauge ground wire from the battery Negative terminal to the Alternator bracket. As the JKs age the small ground straps the ground the engine to the body/frame corrode and break leaving the engine improperly ground which can cause gremlins such as yours.

JKU07

Thanks Jeff. When I unplug the oil sensor, the light stays on.( as I understand it, this is supposed to be that way). The wire travels up the passenger exhaust manifold and into a split harness behind the thermostat. From there it's difficult to say......but I'll keep at it and report back.

Is there anywhere to find a wiring schematic for the JK?

Thanks

jtphoto JK

Did you get a chance to try the extra ground wire. ?

JKU07

Not yet, as i checked the grounds going in/out of the PCM.

I did however discover that the purple/yellow wire that runs into the oil sending unit is not getting power.

i.e.: It does not light up when i put a test light to it. Im not sure if it normally has power running through it....

zstairlessone

In very large (and very expensive) engines the oil pressure low sensor is not at the pump discharge, but at the end of the pressurized supply. This is to protect all parts of the engine from a loss of oil accident not just a failed pump accident.

If this engine is like that (I don't know where the sensor is) then you may have a loose bearing (or other issue) and might be living on borrowed time.

Pull your oil filter (and replace it) and cut the can off of it. Look to see if you have any metal in it, tin, lead or brass.

jtphoto JK

It's not the ground to the PCM I am concerned with it's the constant ground to the Oil pressure switch itself through the engine block.

JKU07

Gotcha. I'll check the ground tomorrow. Although, as of today, there is a faint whining from the timing chain/camshaft area. The whine is non-existent at idle, and increases with rpm's. Since the Oil pump is behind the timing chain cover, this is likely more than a co-incidence.

i'll check the ground first though.

jtphoto JK

If the mechanical oil pressure gauge says there is pressure I would certainly believe that over an electric signal.

jtphoto JK

What is the progress with your problem?