JCB Engine Fault Derate
When a fault is detected, the ECU determines the severity of the fault and may take action to protect either the engine or the machine from potential damage.
The ECU can decide on four possible actions.
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JCB Derate Background Information
The Tier 4 Final / Stage 4 legislation imposes a strict NOx emissions limitation which is achieved via the SCR Aftertreatment system. In order to preserve the Aftertreatment systems ability to reduce NOx, an inducement strategy has been implemented that uses a diagnostic warning and engine speed/ torque derate system so as to minimise the opportunity for an engine to run with reduced emissions control.
The main faults that result in inducement strategy include:
- DEF tank level
- DEF quality
- DEF dosing interruption
- Aftertreatment system tampering
- Exhaust Gas recirculation (EGR) flow – emissions system fault
Figure 1 – DEF tank Level Inducement Summary
JCB Derate Behavior Overview
Once the engine ECU or after-treatment DCU detects any of the faults above, the inducement timer begins. Should the fault remain, a series of torque and engine speed derates shall follow.
1 To start with, there is a 2 hour warning period. During this time the emissions warning lamp will flash amber.
2 Following this there will be a first level derate request. The level 1 torque request (25% reduction) takes 25 minutes to come into action. During this time the emissions warning lamp will be solid amber.
3 After 4 hours from when the inducement was first set, the final derate (forced idle) will be requested. This takes 30 minutes to come into action.
When there is a loss of CAN communication between the engine ECU and after-treatment DCU or when there is a power mismatch in the software contained within the engine ECU and aftertreatment DCU, the machine will immediately derate to idle (20% power).
For DEF tank level the warning, level 1 and level 2 derate are requested at 10%, 5% and 0% respectively.
JCB Fault Clearance:
When inducement faults are cleared, the system will require the machine to go through an ECU power latch cycle, in order to restore full power. If the machine has not been through a power latch cycle, the machine will continue to derate until the inducement has been enacted regardless of the faults been cleared. For more information on the power latch see the engine help files.
NOTE – Inducement will be cleared automatically with a power latch cycle.
When inducement faults are cleared, the system will require the machine to go through a key cycle, in order to reinstate full power. If the fault is healed in the current key cycle, full power will be returned in the next key-cycle to heal the fault and the second to return power. The final key-cycle (once the fault is healed) does not required full power latch.
NOTE – To reinstate power following a DEF level inducement, 2 key-cycles are required.
Re-active Fault within 40 engine running hours:
Should any fault within the same inducement group become re-active within 40 engine running hours, final inducement (idle) shall be requested and enacted within 30 minutes of the re-activated fault occurring
More topics for JCB machine,please refer to:JCB Machine Trouble Repair.