Detroit DD16 GHG14 (2014-16) Fault Code: SPN 1659 FMI 1 (MCM) Thermostat Monitor Error Detected

DESCRIPTION:
Thermostat error detected.

MONITORED PARAMETER:
Coolant inlet temperature sensor.

TYPICAL ENABLING CONDITIONS:
Always enabled

MONITOR SEQUENCE:
None

EXECUTION FREQUENCY:
Once per drive cycle.

TYPICAL DURATION:
30

DASH LAMPS:
MIL

VERIFICATION:
1. Allow engine to cool down such that coolant inlet temperature is less than 50°C (122°F).
2. Drive vehicle for 30 minutes.
3. Preferably with a trailer (loaded or unloaded).
4. Do not idle engine except when necessary.

NOTE: If any other cooling system codes, fix those first.

PROBABLE CAUSES:
1. Engine cooling system thermostat.
2. Inlet and/or outlet coolant temperature sensor.
3. Inlet and/or outlet coolant temperature sensor harness/connector.