Detroit DD15 GHG14 (2014-16) Fault Code: SPN 1325 FMI 31 (MCM) Idle Smoothness Control/Cylinder #3 Misfire at Idle

DESCRIPTION:
This fault code sets when the motor control module (MCM) detects that cylinder #3 has low rpm speed with the injector commanded to max fueling for a count of two with all conditions met.

MONITORED PARAMETER:
Engine rpm

TYPICAL ENABLING CONDITIONS:
1. Engine speed steady between 600 to 950 rpm.
2. Engine coolant temperature between 65°C (149°F) and 114°C (237°F).
3. Engine fuel temperature between 0°C (32°F) and 150°C (302°F).

MONITOR SEQUENCE:
None

EXECUTION FREQUENCY:
Once per drive cycle when enabling conditions are met.

TYPICAL DURATION:
5 seconds

DASH LAMPS:
1. CEL
2. MIL

ENGINE REACTION:
25% Derate

VERIFICATION:
Ensure the ignition has been off for a minimum of 5 minutes prior to the last ignition on. Meet all enabling conditions. Let the engine idle for 5 minutes. (Fault code status will become pending with one detected failure and active with second).

NOTE: Do not use the idle speed balance (ISB) test in the diagnostic service tool for any misfire at idle testing.

POSSIBLE CAUSES:
1. Valve lash out of adjustment.
2. Valve train damage/failure.
3. Bent valve.
4. Valve face/ seat damage.
5. Stuck Jake brake.
6. Bearing failure.
7. Bent connecting rob.
8. Cylinder liner damage.
9. Piston ring damage.
10. Failed cylinder head gasket.
11. Failed fuel injector.

PROBABLE CAUSES:
1. Cylinder kit failure.
2. Valve train failure.
3. Lash adjustments.
4. Fuel injector.
5. High pressure fuel line (rail to fuel injector).
6. Debris entering fuel injector.
7. Fuel quality.

Note: If 1322-31 active, fix that first.