Land Rover Discovery Owners & Service Manuals

Land Rover Discovery: Diesel Exhaust Fluid (DEF) Level / Quality.16 MY EU  A 16 MY NAS  A

Diesel Exhaust Fluid (DEF) Level .16 MY EU  A 16 MY NAS  A

Diesel Exhaust Fluid (DEF) Level .16 MY EU  A 16 MY NAS  A

The level of DEF in the tank is checked via the Instrument Cluster (IC) menu.

When selected the message centre displays the approximate amount of DEF remaining, providing an estimated km/miles figure remaining, prior to emptying the tank

The DEF tank is fitted with combined temperature/ultrasonic level sensors.

Circuit continuity and plausibility of the signals received are checked within the ECM. An ultrasonic "no echo malfunction" is set if no valid echo from the ultrasonic sensor is detected during a predefined time. This typically happens when the ultrasonic signal of the sensor is blocked, or if the DEF tank is overfilled (the air pocket at the top of the DEF tank is no longer present). The vehicle message centre display's an advisory/warning system, which activates in low DEF conditions. If no corrective action is made, the engine will eventually not restart. The stages in the warning system are listed in the following tables

NOTE:

None of the listed stages will activate the MIL. The stages are automatically cleared if the DEF level is increased

Diesel Exhaust Fluid (DEF) Level .16 MY EU  A 16 MY NAS  A

Diesel Exhaust Fluid (DEF) Level .16 MY EU  A 16 MY NAS  A

Diesel Exhaust Fluid (DEF) Quality. .16 MY EU  A 16 MY NAS  A

Diesel Exhaust Fluid (DEF) Quality. .16 MY EU  A 16 MY NAS  A

Diesel Exhaust Fluid (DEF) Quality. .16 MY EU  A 16 MY NAS  A

The DEF quality is monitored after refilling of the DEF tank. The monitoring begins when refilling is identified. In order to recognise a poor quality DEF, the OBD system uses the SCR catalytic converter NOx efficiencies, returned by the passive SCR catalytic converter monitoring, to build long and short term records of the average NOx conversion efficiencies. If the short term record becomes significantly different to the long term record, the malfunction is attributed to the quality of the DEF. The message centre warning system is activated when such a malfunction is detected.

Simultaneously, the MIL is directly activated on the first occurrence of the malfunction detection

Diesel Exhaust Fluid (DEF) Quality. .16 MY EU  A 16 MY NAS  A

Diesel Exhaust Fluid (DEF) Quality. .16 MY EU  A 16 MY NAS  A

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 . 1 6 MY EU   A 16 MY NAS   A

DIESEL EXHAUST FLUID ( DEF ) SUPPLY AND METERING SYSTEM MALFUNCTIONS . 1 6 MY EU   A 16 MY NAS   A

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 . 1 6 MY EU   A 16 MY NAS   A

DIESEL EXHAUST FLUID ( DEF ) SUPPLY AND METERING SYSTEM MALFUNCTIONS . 1 6 MY EU   A 16 MY NAS   A

DIESEL EXHAUST FLUID ( DEF ) SUPPLY AND METERING SYSTEM MALFUNCTIONS . 1 6 MY EU   A 16 MY NAS   A

DIESEL EXHAUST FLUID ( DEF ) SUPPLY AND METERING SYSTEM MALFUNCTIONS . 1 6 MY EU   A 16 MY NAS   A

DIESEL EXHAUST FLUID ( DEF ) SUPPLY AND METERING SYSTEM MALFUNCTIONS . 1 6 MY EU   A 16 MY NAS   A

DIESEL EXHAUST FLUID ( DEF ) SUPPLY AND METERING SYSTEM MALFUNCTIONS . 1 6 MY EU   A 16 MY NAS   A

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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