Make: Detroit
Engine: DD15 GHG17 (2017 & Newer)
PID: N/A
SPN: 1659
FMI: 7
Description: Thermostat Cool Down
Troubleshooting:
DESCRIPTION:
This fault sets when the engine coolant temperature is not maintained to match a modeled
temperature range.
MONITORED PARAMETER:
Inlet coolant temperature and outlet coolant temperature.
TYPICAL ENABLING CONDITIONS:
1. Vehicle speed greater than 45 km/hr. (27 mph)
2. Engine run time after engine start greater than 5 min.
MONITOR SEQUENCE:
None
EXECUTION FREQUENCEY:
Continuous when enabling conditions met.
TYPCIAL DURATION:
Five seconds
DASH LAMPS:
MIL
ENGINE REACTION:
None
VERIFICATION:
Road test the vehicle for 40 minutes.
POSSIBLE CAUSES:
1. Faulty thermostat.
2. Aftermarket components plumbed into the cooling system.
Make: Detroit
Engine: DD15 GHG17 (2017 & Newer)
PID: N/A
SPN: 1659
FMI: 17
Description: Coolant Temperature Low Pre Fail
Troubleshooting:
DESCRIPTION:
This fault sets when the engine coolant temperature has not increased to match a modeled
temperature range.
MONITORED PARAMETERS:
Coolant temperature
TYPICAL ENABLING CONDITIONS:
1. Ambient temp greater than -8°C (18°F).
2. Ambient pressure greater than 755 mbar (11 psi).
3. Vehicle speed greater than 45 km/hr. (27 mph).
4. Engine run time after engine start greater than 5 min.
MONITOR SEQUENCE:
None
EXECUTION FREQUENCEY:
Continuous when enabling conditions met.
TYPCIAL DURATION:
five seconds
DASH LAMPS:
None
ENGINE REACTION:
None
VERIFICATION:
None
POSSIBLE CAUSES:
Fault codes need erasing.
Make: Detroit
Engine: DD15 GHG17 (2017 & Newer)
PID: N/A
SPN: 1659
FMI: 31
Description: Thermostat Cool Down
Troubleshooting:
DESCRIPTION:
Engine coolant temperature not matched.
MONITORED PARAMETER:
Outlet coolant temperature.
TYPICAL ENABLING CONDITIONS:
Always enabled
MONITOR SEQUENCE:
None
EXECUTION FREQUENCEY:
Always enabled
TYPCIAL DURATION:
Two seconds
DASH LAMPS:
None
ENGINE REACTION:
None
VERIFICATION:
None
NOTE: This fault code is an informational/silent fault code. This fault code sets when the
coolant temperature is not within a calibrated threshold, which starts another monitor to
determine if there is a cooling system concern present.
POSSIBLE CAUSES:
Fault codes need erasing.
Make: Detroit
Engine: DD15 GHG17 (2017 & Newer)
PID: N/A
SPN: 1663
FMI: 7
Description: Optimized Idle Safety Loop Faulted
Troubleshooting:
DESCRIPTION:
Optimized idle safety loop faulted.
MONITORED PARAMETER:
Optimized idle safety loop (parking brake, hood tilt switch, neutral safety switch and vehicle
speed).
TYPICAL ENABLING CONDITIONS:
Fault is set active if a maximum number of vehicle speed sensor pulses during an optimized
idle engine start is exceeded or the vehicle speed is above 0.25 Km/H or the engine torque is
above a calibrated threshold for 2 seconds.
MONITOR SEQUENCE:
None
DASH LAMPS:
CEL
ENGINE REACTION:
None
VERIFICATION:
Run an optimized idle mode.
NOTE: When creating log files for optimized idle issues using the diagnostic service tool, add
the J1939 connection. This will created larger log files but the information needed will be
available to reduce troubleshooting time.
POSSIBLE CAUSES:
Faulty Optimized Idle Safety Loop component.