Diesel Exhaust Fluid Quality (Part 1)
The DEF quality is monitored after refilling of the DEF tank. The monitoring begins when refilling is identified. In order to recognize 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 center warning system is activated when such a malfunction is detected. Simultaneously, the MIL is directly activated on the first occurrence of the malfunction detection
| STAGES | CAUSE | WARNING | MESSAGE | DESCRIPTION |
|---|---|---|---|---|
| Stage 1 | Incorrect DEF quality is detected | Amber symbol | Incorrect Diesel Exhaust Fluid quality detected | The DEF does not meet manufacturer specifications. The system must be checked by a Jaguar Land Rover service department |
| Stage 2 | Incorrect DEF quality is detected | Amber symbol | No engine restart possible in 515mls/830km. Incorrect Diesel Exhaust Fluid quality detected | The DEF does not meet manufacturer specifications. The system must be checked by a Jaguar Land Rover service department |
| Stage 3 | Incorrect DEF quality is detected | Amber symbol | No engine restart possible soon. Incorrect Diesel Exhaust Fluid quality detected | The DEF does not meet manufacturer specifications. The system must be checked by a Jaguar Land Rover service department |
| Stage 4 | Incorrect DEF quality is detected | Red symbol | No engine restart possible. Incorrect Diesel Exhaust Fluid quality detected | The DEF does not meet manufacturer specifications. The system must be checked by a Jaguar Land Rover service department |
Diesel Exhaust Fluid 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 through 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