Variant 1: T131, NOx sensor downstream of the particulate filter, not responding
Applies to: EMS10
What does Scania EMS fault code 8704 mean?
The NOx sensor is not responding in time.
What causes Scania DTC 8704?
- Fault in harness-to-component connectors or cable harness. - Fault in the voltage supply to the NOx sensor.
How to fix Scania EMS fault code 8704?
- Check the harness-to-component connectors and cable harness.
- Renew NOx sensor.
Variant 2
Applies to: EMS S6 IoM singlespeed (S6IM)
Detection
The voltage in the circuit has been above the permitted level.
Possible cause
Possible causes: - Open circuit in the charge air pressure sensor circuit. - Fault in the circuit of the coolant temperature sensor, charge air temperature sensor or the extra analogue input.
System reaction
There is a common voltage supply for the charge air pressure sensor, coolant temperature sensor, charge air temperature sensor and the extra analogue input. If a fault occurs in one of the components, this can affect the circuits of the other components. If the voltage is outside the permitted range, the control unit uses a pre-programmed value. An active fault code limits the maximum engine torque by approximately 30%. The engine also responds more slowly than normal to throttle actuation. This is because the smoke limiter is not operating correctly.
How to fix
Check the charge air pressure sensor, coolant temperature sensor, charge air temperature sensor and the component which is connected to the extra analogue input and the harness-to-harness connectors and electrical cables in the circuit.
Variant 3: SCR - NOx sensor after the catalytic converter
Applies to: EMS S6
Detection
The SCR control unit has received a message from the NOx sensor that there is an open circuit.
Possible cause
Open circuit in the NOx sensor circuit.
System reaction
Functions in the SCR system are not affected. 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% after the engine has been running for 50 hours. 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.
How to fix
- Check the circuit components, harness-to-harness connectors and electrical cables.
- 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.
Variant 4
Applies to: EMS S6 (EMS S6 EuroIII)
Detection
The voltage in the circuit has been above the permitted level.
Possible cause
Possible causes: - Open circuit in the charge air pressure sensor circuit. - Fault in the circuit of the coolant temperature sensor, charge air temperature sensor, fuel supply pressure sensor or fan speed sensor.
System reaction
There is a common voltage supply for the charge air pressure sensor, coolant temperature sensor, charge air temperature sensor, fuel supply pressure sensor and fan speed sensor. If a fault occurs in one of the sensors, the other sensor circuits may be affected. If the voltage is outside the permitted range, the control unit uses a pre-programmed value. An active fault code limits the maximum engine torque by approximately 40%. The engine also responds more slowly than normal to throttle actuation. This is because the smoke limiter is not operating correctly. For engines with EGR, the engine runs with EGR but without any feedback from the mass flow sensor. This means that the control unit only makes a rough adjustment of EGR content using predefined values for the position of the EGR damper. Calibration of the mass flow sensor is 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 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.
How to fix
- Check the charge air pressure sensor, coolant temperature sensor, charge air temperature sensor, fuel supply pressure sensor and fan speed sensor, along with the harness-to-harness connectors and electrical cables in the circuits.
- Proceed as follows to verify that the fault has been rectified: Start the engine and run it at idling speed for at least 15 seconds.
- 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.
Variant 5: NOx sensor T115 downstream of the SCR catalytic converter measures too low a value.
Applies to: EMS S8
Detection
NOx sensor T115 downstream of the SCR catalytic converter signals internal fault in the NOx sensor.
Possible cause
Internal fault, open circuit in the electrical circuit, in NOx sensor T115, damaged cable harness between the NOx sensor control unit and gauge or fault in the CAN communication.
System reaction
The fault affects the engine's nitrous oxide emissions. Depending on the emission class, it will result in torque reduction, speed limitation and a warning indication.
How to fix
- Remove the NOx sensor and inspect the damage to the cable harness between the NOx sensor control unit and the gauge.
- If damage is found on the cable harness rectify the cable harness so that the new NOx sensor is not damaged.
- Renew NOx sensor.
- The NOx-sensor only has to be plugged in electrically to verify that the fault has been resolved.
- Check that the fault has been rectified as follows:
- Switch off the power with the starter key.
- Wait until the button for the hazard warning signal has been extinguished.
- Switch on the power with the starter key.
- Check that the fault code has been deactivated.
- Clear the fault code.
- Switch the power off and on with the starter key 3 times to extinguish the emissions warning lamp.
- Wait until the hazard warning signal button has been extinguished between each turn.
This information is for guidance only. Always follow the manufacturer workshop manual and safety procedures; if in doubt, contact an authorised workshop.