PCM 409 Low Fuel Pressure

[DkLkSkr]

Have a 2017 Malibu with the PCM 409 6L engine. Got a low fuel pressure warning that only comes on when at full throttle. No loss of power when pulling skier up or maintaining 34 or 36 mph. Around 730 hours on the engine. Thoughts on why this is only happening at full throttle? Fuel pump issue, fuel filter, or fuel pressure regulator? Would this be hard to fix diy?  I do not believe there is a fuel control cell on these motors that I can find....  Is the inline filter for the gas tank under the rear floor board behind the engine?

[justgary]

6 hours ago, DkLkSkr said:

Thoughts on why this is only happening at full throttle?

It should be obvious that the engine demands the most fuel at WOT.  If the filter (or fuel line) is clogged or the pump is weak, it should show up at high engine load first.

[csleaver]

An alarm and active fault code SPN 94 FMI 1 occurs if the fuel pressure sensor reads below 55 PSI.  Normal fuel pressure should be 59-62 PSI.  Restricted fuel filters or fuel lines, faulty fuel pump, faulty fuel pressure sensor or wiring/connections can cause that fault.

A mechanical fuel pressure gauge can be connected to the fuel rail to confirm the fuel pressure.  If one of the two fuel pumps on the in tank assembly fails, you may find a noticeable pressure loss at wide open throttle, but the engine may still run well at lower speeds.  A quick and dramatic loss of fuel pressure at key off is a common symptom of a failed fuel pump.  The fuel pump assembly has two fuel pumps, filters, pressure regulator, and is normally replaced as a complete assembly.  Be sure to use new pump and mounting screw rubber gaskets when replacing a pump assembly and I highly recommend pressure testing the fuel tank and checking for leaks before operating the boat, afterwards. 

Check the fuel pump1 and fuel pump2 fuses in the engine fuse relay box.  Disconnect and reconnect the fuel pressure sensor plug a couple times.  Check your main power and ground connections at the starter, on the power distribution post, and on the port engine block ground.  Also check that your system voltage is in the normal 13.5-14.5 VDC range.  The fuel pressure sensor runs on the 5 volt reference sensor circuit and a loose or corroded connection can cause enough of a voltage drop to cause the sensor return voltage to be out of range.

[DkLkSkr]

Could octane level cause this type of engine code?  I'm using the manufacture recommended level, but would premium cause this to go away?

[justgary]

7 hours ago, DkLkSkr said:

Could octane level cause this type of engine code?  I'm using the manufacture recommended level, but would premium cause this to go away?

Octane is related to the flash point of fuel.  Low pressure is not related to the fuel, it is either a mechanical or sensor issue.