The function diagram for the IST system includes the following:
• Electronic Service Tool (EST)
• Intake Air Temperature (IAT) sensor
• ENGINE lamp (red)
IST Operation
The IST is an optional feature that allows the ECM to shutdown the engine when an extended idle condition occurs. The idle timer can be programmed for the customer to automatically shut the engine down for idle times that range from 2 to 120 minutes.
Before engine shutdown, the red ENGINE lamp will illuminate. The lamp will flash for 30 seconds to warn
the operator the engine is approaching shutdown.
Idle time is measured from last clutch or brake pedal transition. The engine must be out of gear for the IST to work.
The IST feature can be programmed to operate at specific ambient air temperatures, allowing engine operation in cold or hot weather. Power Takeoff (PTO) applications can be programmed to disable the IST feature for load levels or when PTO features are active.
The resets for the IST include:
• PTO is active.
• Engine speed is not at idle speed (700 rpm).
• Vehicle movement or a Vehicle Speed Sensor (VSS) fault is detected.
• Engine coolant operating temperature is below 60 °C (140 °F).
• Ambient air temperature is below 16 °C (60 °F) or above 44 °C (110 °F).
• Brake pedal movement or a brake switch fault is detected.
• Clutch pedal is depressed or a fault for the clutch pedal switch is detected (manual transmissions, if equipped with clutch switch).
• Shift selector is moved from neutral or park (automatic transmissions).
The IST feature provides several advantages when enabled. Reduced emissions, fuel consumption, and engine wear are all direct results from the IST strategy.
There are four states of the IST electronic operation.
• Idle shutdown timer indicates to the on-board electronics that the vehicle has the following features:
• OFF – turned off at all times.
• PTO available – allows prolonged engine idle shutdown when engine is in low idle and PTO is disabled.
• No engine load – allows prolonged engine idle shutdown when engine is in low idle / no load condition.
• Tamper proof – prohibits operator over-ride.
• Idle shutdown time indicates the programmed value of engine idle time before engine will shutdown.
• Maximum ambient intake air temperature indicates maximum value of ambient intake air temperature programmed to shutdown engine. This feature prevents engine shutdown due to air conditioner usage.
• Minimum ambient intake air temperature – indicates minimum value of ambient intake air temperature programmed to shutdown engine. This feature prevents engine shutdown due to cold ambient temperature.
Fault Detection / Management
The IST feature is internal to the ECM. The subsystems that contribute to the IST strategy have their own fault codes. The fault code for the IST is not a system diagnostic trouble code. The IST fault code is only set to indicate that the IST has been activated and the engine has shutdown.
IST Diagnostic Trouble Codes (DTCs)
DTCs are read using the EST or by counting the flashes from the amber and red ENGINE lamp.
DTC 324
IST enabled engine shutdown
• DTC 324 is set by the ECM when the engine has been shutdown due to exceeding the programmed idle time criteria. The IST feature must be enabled for DTC 324 to be displayed.
NOTE: DTC 324 does not indicate any system or circuit DTCs. Diagnostic checks are not required for DTC 324.
Tools
• EST with MasterDiagnostics® software
• EZ-Tech® interface cable
