13929A 2 Mercruiser COVER (USE WITH 12-3/4" FLYWHEEL)

Hydrocarbon Mitigation
Hydrocarbon (HC) mitigation is intended to protect after treatment hardware from excessive hydrocarbon loading during prolonged periods of low load conditions. Exhaust temperatures that do not properly support the conversion of hydrocarbon in the diesel oxidation catalyst can lead to potential performance issues. These issues can result in failure of CEM components. For this strategy to activate pin 46 on the J1/P1 connector must be grounded. When enable conditions are met, the Engine Control Module will elevate the engine speed and enable bank to bank cylinder cutout to elevate exhaust temperature.Ground pin 46 on J1/P1 connector as frequent as operationally feasible. On applications that require speed control of the engine, grounding pin 46 when in park and/or not working is recommended. On applications that can be controlled independent of engine speed, grounding pin 46 is always recommended. In such an instance, the machine can work while the HC mitigation strategy is in effect (running on 6 cylinders). The remaining 6 cylinders will activate as required to support the desired load.Note: When Pin 46 is grounded, the grounding is acknowledging that permission to elevate engine speed by the engine ECU is acceptable by the operator.Before HC Mitigation is active, the strategy completes the initial checks that include a 15 minute startup delay. Following are the HC Mitigation enablement conditions. If these enable conditions are not met, HC Mitigation will not start.
Coolant Temperature greater than 50° C (122° F)
Exhaust Temperature less than 650° C (1202° F)
Electronic Technician Service mode not active
Pin 46 on J1/P1 grounded
2 or less injector faultsThe following are the conditions to activate HC Mitigation:
Low Exhaust Temperature Level 2 event is active (SPN 173-18)
Or, Low IMAT Level 2 Event is active (SPN 1636-18)
Or, Exhaust Temperature is less than 325° C (617° F) for 1 cumulative hour, without Exhaust Temperature that is greater than 325° C (617° F) for 10 continuous minutes. Cumulative hour will continue to count during 10 minute debounce.
Pin 46 J1/P1 groundedOnce the above conditions are met, the engine ECU will set minimum engine speed to 1000 rpm. The below flowchart explains the general operation of HC Mitigation Strategy.
Illustration 1 g06317097If HC Mitigation fails, Low Exhaust Temp Level 2 Event (SPN 173 – 18) is activated. All cylinders will be enabled, and engine speed will be set to Low Idle or customer demanded speed. 1 hour after the failure, the engine ECU will attempt another HC Mitigation cycle. If 3 complete cycles of HC Mitigation run without success, the Low Exhaust Temp Level 3 event (SPN 173-1) will activate. As a result, the engine will shut down.If HC Mitigation is successful, the Warm Cycle will be enabled. Warm Cycle is defined as a 20 minute period consisting of two 10 minute periods. The first 10 minute period will disable fuel to one bank while continuing to deliver fuel to the other. The second 10 minute period will reverse this process by switching banks. This procedure is also referred to as bank to bank mode. The engine bank consists of the Left Hand and the Right-Hand sides of the engine. In Warm Cycle, the engine will continue to run bank to bank cylinder cutout mode and will maintain the last minimum engine speed request. After 4 Warm Cycles, Low Exhaust Temp Level 2 event will be reset. The engine will continue to run Warm Cycle indefinitely until the pin 46 is open or reset if key cycled.Note: Refer to the Troubleshooting guide for information about Low Exhaust Temperature and Low IMAT events.