Communication fault in the SCR system
Clear the fault code memory and try to start the engine.Check fuses.Check for CAN communication fault codes in other control units at the same time. Troubleshoot these first.Check the electrical cables and clean the connectors.If this does not help, check that the SCR control unit and NOx sensor are receiving voltage off/on (U15) at the same time. If the above action does not help, first renew the NOx sensor, and if this does not help renew the SCR control unit. It is, however, very unusual for there to be a fault on the SCR control unit. Make sure that the fault is not caused by something else before renewing the SCR control unit.Inactive fault codes are seldom the main cause of faults. Always troubleshoot active fault codes first.When troubleshooting inactive fault codes: Check that the fault codes have not been generated during a workshop visit or when switching off the main power switch by going to More information and checking whether the vehicle speed was 0 or 15 and the engine speed was 0 when the fault code was generated.Also check whether the fault code has been generated by low voltage by checking whether the voltage was below 22 V when it was generated.Proceed as follows to verify that the fault has been rectified:Switch the power off and on with the starter key. 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 3 times in succession at 10 second intervals to extinguish the warning lamp.
What you'll see
No driver-visible symptom recorded.
System reaction
No system-reaction text recorded.
Diagnostic depth
The engine control unit has no CAN message from the NOx sensor. If the vehicle is equipped with an SCR-system, the CAN message should be transmitted via the SCR control unit.
If the fault code is generated frequently, this is probably due to a fault in the cable harness or connectors.Communication between the engine control unit and the SCR control unit or between the SCR control unit and the NOx sensor has been interrupted.If fault code 4108 has been set at the same time, there is probably a problem in the communication between the engine control unit and the SCR control unit. If fault code 4108 was not set at the same time, there is probably a fault in the communication between the SCR control unit and the NOx sensor. If fault code 5657 or 8263 has been generated at the same time, start by troubleshooting from them initially.If the fault code has been generated once, this may be because the voltage to the NOx sensor has been interrupted at the same time as the SCR control unit has been supplied with voltage.The SCR control unit in the main unit may be defective.The connector has been disconnected with the power on or when reprogramming the control unit at the workshop.Low battery voltage.