DEF Warnings and Engine Limits
Important: Ignoring the DEF warning lamps and not refilling the DEF will result in limited engine power with a speed limit of 5 mph (8 km/h) eventually being applied. For Cummins engine service literature, refer to the Cummins Online website, see https://www.cummins.com/support/manuals or scan the QR code. See Fig.. For Detroit engine service literature, refer to the Detroit Diesel link on the DTNA TechLit website, see https://www.dtnatechlit.com/portal-public or scan the QR code. See Fig..
Fig. 1, Cummins QR Code
Fig. 2, TechLit QR Code
DEF Level LowInitial Warning
When the DEF level reads low the following warnings strongly encourage the driver to refill the DEF tank. See Fig..
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The CHECK engine lamp flashes for 30 seconds when the vehicle is started.
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The DEF warning lamp illuminates.
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One bar of the DEF-level lightbar illuminates solid amber.
The DEF tank must be filled to cancel the warning sequence.
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DEF Warning Lamp (illuminates constantly)
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DEF-Level Lightbar (1 bar solid amber)
Fig. 3, DEF Level LowInitial Warning
DEF Level LowCritical Warning
When the DEF level reads low, the following warnings are activated. See Fig..
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The CHECK engine lamp flashes for 30 seconds when the vehicle is started.
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The DEF warning lamp illuminates.
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One bar of the DEF-level lightbar flashes red.
Engine performance is limited, with progressively harsher engine power limits applied.
The DEF tank must be filled to cancel the warning sequence.
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DEF Warning Lamp (illuminates constantly)
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DEF-Level Lightbar (1 bar flashing red)
Fig. 4, DEF Level LowCritical Warning
DEF Empty
When the DEF level reads empty, the following warnings are activated. See Fig..
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One bar of the DEF-level lightbar flashes red.
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The DEF warning lamp flashes.
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The CHECK engine lamp illuminates.
Engine performance is limited, with progressively harsher engine power limits applied.
The DEF tank must be filled to cancel the warning sequence.
Note: Engine performance is limited.
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DEF Warning Lamp (flashing)
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DEF-Level Lightbar (1 bar flashing red)
Fig. 5, DEF Empty Warning
DEF Level Empty and Ignored
If the empty warning is ignored and the DEF is not refilled, the DEF warning lamp flashes, one bar of the DEF-level lightbar flashes red, and the red STOP engine lamp illuminates in addition to the CHECK engine warning lamp. See Fig..
If the DEF tank is not refilled, a 5 mph (8 km/h) speed limit will be applied after the next engine shutdown, or while parked and idling.
Note: The STOP engine, CHECK engine, and DEF lamps illuminate, engine power is limited, speed limit of 5 mph (8 km/h).
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DEF Warning Lamp (flashing)
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DEF-Level Lightbar (1 bar flashing red)
Fig. 6, DEF Empty and Ignored Warning
DEF Quality or SCR Tampering
Notice: Once contaminated DEF or tampering has been detected in the SCR system, the vehicle must be taken to an authorized service center to check the SCR system for damage, and to deactivate the warning lamp and engine limits.
If contaminated DEF or tampering is detected, the DEF warning lamp flashes, and engine power is limited with progressively harsher limits applied. If the fault is not corrected, the STOP engine lamp illuminates and a 5 mph (8 km/h) speed limit is applied after the next engine shutdown, or while parked and idling. See Fig..