Land Rover Discovery Owners & Service Manuals

Land Rover Discovery: Diesel Exhaust Fluid ( DEF ) Quality. 16 MY NAS   B - 17 MY NAS  B

Diesel Exhaust Fluid ( DEF ) Quality. 16 MY NAS   B - 17 MY NAS  B

Diesel Exhaust Fluid ( DEF ) Quality. 16 MY NAS   B - 17 MY NAS  B

Diesel Exhaust Fluid (DEF) Quality

Prior to the NOx sensor and the monitoring function becoming operational, the sensor must have reached its 'dew point'. This is the point where the moisture content in the exhaust gas has evaporated and can no longer damage the NOx sensor. In normal ambient conditions, this process typically takes around 6 to 10 minutes. If a malfunction is detected during the operation of the NOx sensor, a reversible fault is stored. If a malfunction is detected over two (NAS variants) or three (EU6 variants) consecutive drive cycles, a permanent fault is stored and the MIL is activated

The following monitoring is performed on the NOx sensors

  • Signal plausibility and correction factor limits
  • Circuit continuity between the sensor control unit and probe element
  • Operating temperature reached after a defined heating period

Private CAN Bus - Monitoring

The following components are connected to the ECM via a private CAN bus. The ECM provides a gateway, for communication to the vehicle CAN bus

  • Heater control unit
  • NOx sensor control unit(s)

The following CAN communication monitoring applies to these components

  • Signal time-out
  • Signal check sum

The DEF injector, DEF pump, temperature and level sensors are hardwired to the ECM and do not involve CAN communication

DIESEL EXHAUST FLUID ( DEF ) SUPPLY AND METERING SYSTEM MALFUNCTIONS . 16 MY NAS  B - 17 MY NAS   B

DIESEL EXHAUST FLUID ( DEF ) SUPPLY AND METERING SYSTEM MALFUNCTIONS . 16 MY NAS  B - 17 MY NAS   B

The OBD system monitors components and the functionality of the DEF supply and metering system. If a malfunction is detected a message centre warning is displayed. If no action is taken to rectify the warning malfunction, this will eventually lead to a 'No engine restart' situation

DIESEL EXHAUST FLUID ( DEF ) SUPPLY AND METERING SYSTEM MALFUNCTIONS . 16 MY NAS  B - 17 MY NAS   B

DIESEL EXHAUST FLUID ( DEF ) SUPPLY AND METERING SYSTEM MALFUNCTIONS . 16 MY NAS  B - 17 MY NAS   B

DIESEL EXHAUST FLUID ( DEF ) SUPPLY AND METERING SYSTEM MALFUNCTIONS . 16 MY NAS  B - 17 MY NAS   B

DIESEL EXHAUST FLUID ( DEF ) SUPPLY AND METERING SYSTEM MALFUNCTIONS . 16 MY NAS  B - 17 MY NAS   B

Diesel Exhaust Fluid (DEF) Supply and Metering System Malfunctions

The following DEF supply and metering system malfunctions may trigger the message centre warning system

  • Pressure build up in the supply line
  • Metering/injection time to closed loop
  • Over pressure in supply line
  • Under pressure in supply line
  • Injection valve open circuit
  • SCR system relay open circuit
  • Solenoid pump(s) open circuit
  • Combined temperature/level sensor open circuit
  • Missing communication with upstream NOx sensor (NAS variants only)
  • Missing communication with downstream NOx sensor

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