DESCRIPTION:
Diesel exhaust fluid (DEF) unit – unable to clear restriction.

MONITORED PARAMETER:
1. DEF pressure.
2. DEF air pressure.

TYPICAL ENABLING CONDITIONS:
Dosing enabled

MONITOR SEQUENCE:
SPN 4335/14 and 31 active.

EXECUTION FREQUENCY:
Continuous when enabling conditions met.

DASH LAMPS:
1. MIL
2. CEL

ENGINE REACTION:
Derate 25%

VERIFICATION:
Selective catalyst reduction (SCR) quantity test.

PROBABLE CAUSES:
1. Failed DEF pressure sensor.
2. DEF metering unit air inlet restricted.
3. Flush the DEF system.
4. Failed diffuser heater.
5. Failed DEF nozzle.
6. Failed supply hose for DEF.