Fault code: EMS 4123 SCANIA

Error identification:

The voltage in the reductant doser voltage supply circuit has been too low.

Cause:

Short circuit to battery voltage in the reductant doser voltage supply circuit.

Notes:

The fault causes reductant injection to be switched off.

The fault affects the vehicle s emissions of nitrogen oxides (NOx) and the lamp which warns about a high level of contaminants comes on in the instrument cluster. A text message is also displayed in vehicles with NOx monitoring.

Vehicles with NOx monitoring

An active fault code limits the maximum engine torque by approximately 40%.

An active fault code cannot be cleared from the control unit. When the fault has been rectified, the control unit must verify that the fault has been rectified in order for the fault code to become inactive.

Action:

Check the reductant doser, its harness-to-harness connectors and electrical cables.

Check the battery voltage.

Proceed as follows to verify that the fault has been rectified:

Switch off the power with the starter key, wait for at least 90 seconds and switch on the power with the starter key again.

If the fault is resolved, 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 turn off the warning lamp.