This fault code is stored when emission of NOx measured by the NOx sensor (F791) exceeds the limit of 5 gr/kWhr.
This fault can result from several mechanical failures. Perform the job ‘Check/flush dosing module, EAS’ to determine a mechanical problem with the EAS dosing module.
The ECS-DC4 electronic control unit also activates the MIL the second time the diagnostics run and fail.
The reason it was re-programmed is DAVIE can not clear the fault,the vehicle does a self NOX monitoring and will extinguish the light when it sees everything ok
The causes are listed below
The MIL cannot be switched off and this fault code cannot be cleared with DAVIE. See ‘Procedures to switch off the MIL’.
AdBlue quality not within the specifications or liquid other than AdBlue present in the AdBlue tank
Too little delivery of AdBlue by dosing module EAS (B494).
AdBlue nozzle plugged (partly).
Mechanical failure of the engine, fuel system or intake/exhaust system
The flush is best done by fill the ad blue air filter with boiling water remove pipe from the nozzle run the engine and after about say 5 mins .I can’t remember the time it should blow the water out with the air ,if it doesn’t the pump unit is U/S …The reason it says NOX high is that the ad-blue side is not working ,the NOX sensor is just doing what it is meant to do