The reductant pump needs to run faster than expected to keep the pressure.
The possible reasons behind this failure can be divided into three groups: 1. Reductant delivering problem 2. Pressure sensor failure 3. Overdosing In order to find the reason behind this fault a number of steps can be taken. 1. Reductant delivering problem. The main cause behind this fault is that the system has problems to push reductant to the dosing unit. o Check that the system is not frozen. o Use the diagnostic tool to run the reductant circuit test and follow the trouble shooting instructions. The instructions will help you to check the following: - The reductant pick-up unit for leakage or clogging. - The suction hose for leakage or clogging, especially between the reductant pick-up unit and the suction hose. - The prefilter and the main filter in the reductant pump for clogging. - Overflow valve in the reductant pump opens too early. - Leakage or clogging in the pressure line between the reductant pump and the dosing unit. - Clogged prefilter in the dosing unit - Broken reductant pump 2. Pressure sensor failure - Use the diagnostic tool to check the reductant pressure sensor value. The sensor reading should be close to the current ambient pressure when the reductant pump has been turned off for several minutes. If not, proceed with trouble shooting the pressure sensor. - Monitor the pressure with the diagnostic tool. Normally the pressure is not completely stable. If for example the pressure seems to be frozen at 100 mbar there might be something wrong with the pressure sensor. If this is suspected, disconnect the hoses to the dosing unit and try to cause a small pressure change at the inlet of the dosing unit. At the same time monitor the pressure with the diagnostic tool and look for a pressure change. If nothing happens the sensor might be broken and the dosing unit should be changed. 3. Overdosing - Disconnect the reductant dosing unit(s) (V117, V231) from the exhaust and perform a dosing accuracy test using the diagnostic tool
What you'll see
No driver-visible symptom recorded.
System reaction
No system-reaction text recorded.
Diagnostic depth
The control signal to the reductant pump (V183) is much higher than normal.
This fault occurs when the system has problem to deliver reductant to the dosing unit or if the pressure sensor in the dosing unit gives a value that is too low or if the reductant dosing unit(s) (V117, V231) are overdosing. Possible failures for the reductant delivering problem are: 1. Leakage or clogging in the suction hose or reductant pick-up unit, between the reductant tank and the reductant pump. 2. Clogged prefilter or main filter in the reductant pump. 3. Overflow valve in the reductant pump opens too early. 4. Leakage or clogging in the pressure line between the reductant pump and the dosing unit. 5. Clogged prefilter in the dosing unit 6. Broken reductant pump