Check that the venting line to the reductant tank is not blocked.Check that there is no frozen reductant in the return pipe. If the reductant is frozen: Check that the coolant level in the engine is not too low.To check that heating of the return line is working. Start the engine and check that the line is getting warm. If not, check that the coolant from the engine is reaching it as it should do.Also check that the solenoid valve is opening fully. If heating is taking place, check whether the return line is blocked.Proceed as follows to verify that the fault has been rectified:Carry out the test "Devalidating fault codes for NOx control" which can be found under the Check tab in SDP3 to check that the fault has been rectified. The test should be carried out outdoors because the exhaust gases become very hot and there is a risk that the exhaust extractor hose will melt. The test may take between approximately 5 to 30 minutes to carry out, depending on which fault codes are active.Otherwise, you can carry out the following so that the control unit will devalidate the fault:Start the engine and switch it off.If the fault has been rectified, the fault code becomes inactive. Clear the fault code.Switch the power off and on with the starter key three times in succession at 10 second intervals to extinguish the warning lamp.

Diagnostic depth