Exhaust Fluid Incorrect
If the system is filled with an incorrect medium, this will become apparent after several hundred miles (kilometers) later by elevated nitrogen oxide values in the exhaust gas despite adequate injection of the supposed urea-water solution. The system recognizes an incorrect medium when certain limits are exceeded. From this point on, a warning and shut-down scenario is also initiated that allows a remaining range of 200 mls.
The exclamation mark in the symbol identifies the fault in the system. In this case, the message in the CID informs the driver to go to the nearest workshop.
Scheme 3
CC message in cluster, range = 0 miles
Scheme 4
CC message in CID, range 0 miles
Scheme 5
CC message in cluster, in case of incorrect DEF
Scheme 6
CC message in CID, in case of incorrect DEF
Refilling
The active and passive reservoirs can be refilled with urea-water solution either by the service workshop or by the customer himself.
The system can be refilled without any problems with the vehicle on an incline of up to 5° in any direction. In this case, 90% of the maximum possible fill is still achieved.
The volume of the urea-water solution reservoir is designed such that the range is large enough to cover one oil change interval. This means the "normal" refill takes place as part of the servicing work in the workshop. If, however, the supply of urea-water solution should run low prematurely due to extraordinary driving profile, it is possible to top up a smaller quantity.
Refilling in Service Workshop
Refilling in the service workshop refers to the routine refill as part of the oil change procedure. This takes place at the latest after
- 13000 mls on the E90
- 11000 mls on the E70 or
- one year.
In this case, the system must be emptied first in order to remove older urea-water solution. This takes place via the extractor connections in the transfer line. Although a small residual quantity always remains in the reservoirs, it is negligible.
Diesel Exhaust Fluid
The diesel exhaust fluid (DEF) is a urea-water solution which acts as a the carrier for the ammonia that is used to reduce the nitrogen oxides (NO x ) in the exhaust gas.
To protect persons and the environment from the effects of ammonia and to make it more easy to handle for transport and refuelling procedures, it is provided in an aqueous urea solution for the SCR process.
The recommended urea-water solution must meet certain standards for quality which are set forth in accordance with the DIN 70070/AUS32.
The DEF is a high-purity, water-clear, synthetically manufactured solution consisting of 32.5% urea with the balance being water (67.5%). The urea-water solution used must correspond to this standard.