DEF Warnings and Engine Limits
Important: Ignoring the DEF low level warnings results in limited engine power, with the application of a 5 mph (8 km/h) speed limit.
DEF Level Low—Initial Warning
When the diesel exhaust fluid (DEF) level is low, the DEF warning lamp illuminates solid amber, and the driver display screen presents an alert. See Fig.. Refill the DEF tank in order to cancel the warning sequence.
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DEF Level Low
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DEF Tank Empty
Fig. 1, DEF Level Messages
DEF Empty
When the diesel exhaust fluid (DEF) level reads empty, the following lamps and messages notify the driver.
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The DEF warning lamp flashes amber.
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The MIL lamp illuminates.
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The driver display screen presents the warning, ‘DEF Tank Empty.’ See Fig..
Power is limited with progressively harsher engine power limits applied.
DEF Tank Empty and Ignored
If the empty warning is ignored and the DEF tank is not refilled, the red STOP engine lamp illuminates in addition to the MIL lamp and CHECK engine lamp (on vehicles with a Cummins ISB or ISC/L engine).
If the DEF is not refilled, a 5 mph (8 km/h) speed limit is applied after the next engine shutdown, while parked and idling, or if a fuel refill is detected.
DEF Contamination or SCR Tampering
Notice: Once contaminated diesel exhaust fluid (DEF) or tampering with the aftertreatment system (ATS) has been detected, the vehicle must be taken to an authorized service facility to check the SCR system for damage and to deactivate the warning lights and engine limits.
If contaminated DEF or tampering with the ATS is detected, the DEF warning light flashes and the MIL lamp illuminates to warn the driver. The CHECK engine lamp also illuminates on vehicles with a Cummins ISB or ISC/L engine.
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Detroit engines: Engine power is limited with progressively harsher limits applied. If the fault is not corrected, the STOP engine light illuminates and a 5 mph (8 km/h) speed limit is applied after the next engine shutdown, while parked and idling, or if a fuel refill is detected.
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Cummins engines: Engine power is limited with progressively harsher limits applied. If the fault is not corrected, the STOP engine light illuminates and a 5 mph (8 km/h) speed limit is applied after the next engine shutdown, or while parked and idling.