Detroit DD15 GHG14 (2014-16) Fault Code: SPN 679 FMI 7 (MCM) Pressure Limiting Valve (PLV) Staying Open

NOTE: The pressure limiting valve will open when rail pressure is above 1150 bar. The motor control module (MCM) will command a lower rail pressure trying to force the pressure limiting valve closed. If the pressure limiting valve does not close, a fault code is generated. The condition that caused the PLV to open must be addressed.

DESCRIPTION:
1. Pressure limiting valve.
2. Failed to close.

MONITORED PARAMETER:
Pressure limiting valve.

TYPICAL ENABLING CONDITIONS:
10 seconds

MONITOR SEQUENCE:
None

EXECUTION FREQUENCY:
Continuous when enabling conditions met.

TYPICAL DURATION:
10 seconds

DASH LAMPS:
1. MIL
2. CEL

ENGINE REACTION:
Derate 25%

VERIFICATION:
Engine Idle: One minute.

NOTE: The PLV will open with rail pressure is above 1150 bar.

PROBABLE CAUSES:
1. If any other codes present, fix those first.
2. If at idle you have above 900 bar, check for damaged needle return line and a damaged line (fuel rail to fuel injector).
3. If at 1800 rpm you have above 900 bar, check for damaged needle return line, damaged amplifier return line, and a damaged line (fuel rail to fuel injector).
4. If fuel pressure stays below 900 bar, replace the PLV.