Scania fault code 4421
Code 4421 is used by 3 different Scania systems. Choose the control unit shown in your diagnostic tool:
EMS Engine Management System
Coolant temperature sensor, unexpectedly low value
The control unit has interpreted the value from the coolant temperature sensor as lower than expected.
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ZF ZF gearbox
Proportional valve D1
Incorrect signal from proportional valve D1.
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AMS
Communication error, requested urea quantity V117 from EMS
The EEC control unit has detected an error in the CAN communication from the EMS control unit regarding the requested urea quantity.
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