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Engine Maintenance and Fuel Monitor Description

The maintenance modes are automated engine run cycles performed to mitigate the potential adverse affects to internal combustion engine (ICE) components due to limited or no engine run time. The engine control module (ECM) monitors ICE run time and fuel age and invokes the engine maintenance mode or the fuel maintenance mode when the threshold criteria is exceeded. Limited engine run time can result in component degradation, combustion by-product (water/fuel) accumulation in engine oil, and stale petrol which can lead to the following conditions:

The maintenance modes are also necessary to exercise emissions related equipment and to reduce the possibility of ICE no-start conditions. The ICE must start every time to prevent the vehicle occupants from being stranded.

Engine Maintenance Mode

The engine maintenance mode will run every 42 days if the ECM determines that the ICE run time has not been sufficient enough to purge the contaminants from the engine oil. The ECM commands the ICE to run for a contaminant burn-off time of at least 30 s after the engine coolant temperature (ECT) reaches 65°C (149°F), unless cold starts have been experienced since the last engine maintenance mode event. Between 15-90 s are added to the required contaminant burn-off time each time all of the following cold start criteria are met:

If an ECT or IAT sensor fault is present at an initial ignition cycle engine run event, a default time will be added to the required contaminant burn-off time.

The ICE runs continuously while the engine maintenance mode is active.

At power down, ICE run time duration above 65°C (149°F) ECT, is subtracted from the required contaminant burn-off time.

The engine maintenance mode timer (days since engine run) is reset to 0 when the required contaminant burn-off time is complete.

Fuel Maintenance Mode

When the ECM determines that the fuel age is greater than 365 days, the ICE will run until the fuel level is less than 1/3 tank. The ICE will cycle ON and OFF and will run as efficiently as possible while the fuel maintenance mode is active.