Replacing the NOₓ Sensor

The service life of the NOX sensor on the CAN bus/NOX sensor module depends on the type installed:

NOX sensor

Service life

P/N 56.03.003

8,000 operating hours with ambient temperature max. +90 °C (+194 °F) at evaluation unit

P/N 56.03.002

6,000 operating hours with average temperature of evaluation unit at +90 °C (+194 °F)

 

After this time the NOX sensor must be replaced. The total operating hours of the NOX sensor are displayed in the Sensor view of the respective NOX monitor (see section Sensor). You obtain a replacement sensor from MOTORTECH.

The replacement of the NOX sensor is detected by the EasyNOₓ and logged in the logbook of the respective NOX monitor.

Proceed as follows to replace the NOX sensor:

  

Operational safety!

To safely dismount the NOX sensor, be sure to observe the following:

  • To protect the NOX sensor and yourself, wear ESD-compliant work gloves. To protect the NOX sensor against electrostatic discharge, also comply with IEC 61340-5-1 and IEC TR 61340-5-2 in their respective valid versions.
  • Under no circumstances touch the probe of the sensing element while dismounting.
  • The NOX sensor must not be live during dismounting and must have cooled down for at least 15 minutes after the voltage has been switched off. Otherwise, touching the sensing element may cause burns, the sensing element may burn, and serious damage to the connected equipment due to sparking or a short circuit may occur.

   

Operational safety!

The NOX sensor must not be used any further under any circumstances if it is damaged or the sensing element of the NOX sensor has been mechanically shocked (e.g. by dropping it on the floor or impacts on the sensing element). In these cases, contact MOTORTECH for sensor replacement (see Customer Service Information).

   

Operational safety!

Proper functioning of the NOX sensor is only guaranteed if the sensing element does not overheat at the mounting location. Avoid accumulated heat at the sensing element and ensure sufficient ventilation of the sensing element by ambient air.

   

Operational safety!

The sensing element of the NOX sensor P/N 56.03.003 may be mounted a maximum of one time, the sensing element of the NOX sensor P/N 56.03.002 a maximum of two times. The electrical connection to the evaluation unit of both NOX sensors may be established and disconnected a maximum of 20 times. After that, proper functioning of the sensor can no longer be guaranteed.

 

  1. First ensure the following:
  2. Then disconnect the connection cable to the CAN bus module from the connector of the NOX sensor's evaluation unit.
  3. Make sure that the sensing element has not been live for at least 15 minutes. Then unscrew the sensing element from the welding boss using a flare nut wrench 22 mm (0.87") with a spared corner wave profile. The outgoing wires must not twist in the process. Therefore counter the sensing element with your hand. Do not use a hammer or a flat spanner to loosen the sensing element.
  4. Dismount the evaluation unit from the mounting plate of the CAN bus/NOX sensor module by loosening the two M8x20 hexagon screws.
  5. Remove the NOX sensor.
  6. At the mounting position of the sensing element, first check the NO2/NOX ratio (correction factor K) in the exhaust gas with a suitable calibrated exhaust gas analyzer. More information on this is available in the section Determining the NO2/ NOₓ Ratio.
  7. Then mount the evaluation unit of the NOX sensor onto the mounting plate of the CAN bus/NOX sensor module using the two hexagon screws M8x20 and a tightening torque of 10 Nm (7.4 lb-ft).
  8. Remove the protective cap from the probe of the new NOX sensor's sensing element. Do not pull on the connection cable, but hold the sensing element only by its metal body.
  9. Check whether the thread of the sensing element is sufficiently greased. If necessary, re-grease only the thread of the sensing element with a small amount of high temperature grease. For NOX Sensor P/N 56.03.003, use only Optimol Paste MF from Castrol® or Never Seez Regular Grade from Bostik® with a recommended amount of 40 mg ± 10 mg.
  10. Also make sure that no dirt, dust, or grease gets deposited in or on the probe during replacement.
  11. Insert the sensing element into the welding boss and screw the sensing element into the welding boss via its hexagon nut by hand first. The outgoing wires must not twist in the process. Therefore counter the sensing element with your hand.
  12. Then, tighten the sensing element over its hexagon nut using a calibrated torque tool with the specified torque as shown in the drawing.

    P/N 56.03.003:

    P/N 56.03.002:

    01_Neigungswinkel-horizontal

    01_Neigungswinkel-horizontal

  13. Then lay the connection cable between the sensing element and the evaluation unit. In doing so, observe the following.

    P/N 56.03.003:
    Comply with the specifications in the section Laying the Connection Cable.

    P/N 56.03.002:
    Make sure that the minimum bending radius of the connection cable of 20 mm (0.79") is observed and that the angle of the cable outlet at the sensing element grommet is less than 15°.
  14. Make sure that the five-pole connector of the NOX sensor's evaluation unit is dry and that there are no particles or deposited grease in the connector.
  15. Connect the connection cable to the CAN bus module to the five-pin connector of the evaluation unit.
  16. After you have put the EasyNOₓ system back into operation, correct the NO2/NOX ratio determined above in the NOX Setup view of the respective NOX monitor in the entry K (see section Preferences), if necessary.
  17. Also, if necessary, correct the NO2 correction factor of the NOX sensor in the NOX Setup view of the respective NOX monitor in the entry KNO2 (see section Preferences).