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C12 Oil Pressure Sensor

Discussion in 'Engines' started by Bayhouse, Nov 14, 2025 at 3:45 PM.

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  1. Bayhouse, Nov 14, 2025 at 3:45 PM
    #1
    Bayhouse

    Bayhouse New Member

    Joined:
    Oct 11, 2020
    Messages:
    37
    Location:
    Brigantine, NJ
    TLDR version - what's the likelihood that the sensor is bad when the engine is intermittently throwing SPN 100 (Oil Pressure)/ FMI 3 (voltage above normal) vs. the harness, something in the ECM or some other gremlin? Oil level is not the issue.

    On my STBD C12 (2005, 705hp), I am getting an intermittent Engine Oil Pressure alarm, SPN 100 / FMI3 (Voltage Above Normal). This diagnostic has even popped up a few times with just the engine switch turned on (engine not running) so it's pretty clearly an electrical issue. Oil level is fine and no other issues with the engine performance.

    When running, if I wiggle the plug on the sensor, the diag will go away for maybe 5 seconds, 5 minutes or the rest of the day. Seems to be more prevalent at low speeds. The only constant now is it WILL happen, we just don't know WHEN.

    I've cleaned/checked every ground I could find, checked the plug wires and plug with no luck. I've debated swapping the sensor with the other engine, but STBD sensor is in between engines and easily accessible when the alarm signals (I get it on my Furuno MFD as well the MPD), on PORT the sensor will be inaccessible on the outboard side when running.

    I have a test procedure from CAT, but I'm a few hundred miles away from the boat and trying to game plan an approach before we jump back aboard and resume our trip South (currently about 1/2 of the way). Also trying to avoid making a lot of changes while on this journey because it is more of a nuisance.

    Fuel and coolant temp sensors have already been replaced on this engine (a few years back) and before I spend the $ on a sensor, was hoping for some opinions about the likelihood that the issue is the sensor vs. something else.

    Thanks!
  2. d_meister, Nov 15, 2025 at 12:04 PM
    #2
    d_meister

    d_meister Senior Member

    Joined:
    Mar 4, 2010
    Messages:
    499
    Location:
    La Conner, WA.
    Be sure to look closely in the plugs that connect to components to be sure the connectors are fully inserted and locked in place. I've encountered OEM connectors where the terminals are pushed back into the connector housings when inserted and barely make contact.
    You can also switch sensors from one engine to the other to verify symptoms.
  3. Bayhouse, Nov 15, 2025 at 12:12 PM
    #3
    Bayhouse

    Bayhouse New Member

    Joined:
    Oct 11, 2020
    Messages:
    37
    Location:
    Brigantine, NJ
    The plug is a deutsch style with the terminals enclosed - is there a good way to test their fit?
  4. d_meister, Nov 15, 2025 at 2:39 PM
    #4
    d_meister

    d_meister Senior Member

    Joined:
    Mar 4, 2010
    Messages:
    499
    Location:
    La Conner, WA.
    They're definitely some of the best connectors available , but I have had some that weren't engaged with the lock tab. You can see pretty much with a glance if a pin or socket isn't at the same levels as the others, and just a nudge with a toothpick or pencil eraser will show if there's a loose one. The silicone weatherseal can hold it in near-position. If it's the type of Deutsch with a locking wedge, it can be pulled out to push the terminal into the locked home position if you encounter one.
    upload_2025-11-15_11-37-26.png
  5. DOCKMASTER, Nov 16, 2025 at 11:10 AM
    #5
    DOCKMASTER

    DOCKMASTER Senior Member

    Joined:
    Feb 26, 2012
    Messages:
    1,609
    Location:
    Ketchikan, Alaska
    Did you try swapping your sender from Port to STBD ? Then see if the issue follows the sender. Honestly, I don't think those senders are very expensive ? I would just replace it to see if that is the issue.
    d_meister likes this.