PLATE 8E9476 - Caterpillar

The air/fuel ratio must be adjusted properly in order to comply with the emissions requirements of the site. The correct air/fuel ratio also helps ensure stable operation.The "Aftertreatment #1 Outlet Oxygen Sensor Voltage Offset" parameter directly offsets the voltage of the map for the "Desired Aftertreatment # 1 Outlet Oxygen Sensor".The map is based on the engine speed and load. Adjustment of the "Aftertreatment #1 Outlet Oxygen Sensor Voltage Offset" causes the air/fuel ratio to be either richer or leaner.The "Aftertreatment #1 Outlet Oxygen Sensor Voltage Offset" has a range of -0.5 V to +0.5 V. The default value is 0.00 V.
A richer air/fuel mixture corresponds to a higher voltage and more CO in the exhaust. Increasing the offset increases the "Desired Aftertreatment # 1 Outlet Oxygen Sensor" voltage. The air/fuel ratio becomes richer.
A leaner air/fuel mixture corresponds to a lower voltage and more NOx in the exhaust. Decreasing the offset decreases the "Desired Aftertreatment # 1 Outlet Oxygen Sensor" voltage. The air/fuel ratio becomes leaner.You can use Caterpillar Electronic Technician (ET) to monitor the actual state and the desired state of several characteristics of engine operation. You can also adjust the parameters.
Illustration 1 g02290457
Illustration of the Cat ET "Calibration" screen
The graph in Illustration 1 shows a locked view of the actual status and the desired status of a parameter. The view is locked and unlocked by selecting the "Hold" button. The "Settings" button controls the grid display, the data points, and the sizes of the axes for parameters, and time. The parameters are selected by using the "Parameters" button. The information in the graph can be displayed as text by selecting the "Text" button.Illustration 1 also shows the "Aftertreatment #1 Outlet Oxygen Sensor Voltage Offset" parameter. The value is changed by typing in the "Value" field. The value can also be changed by using the up arrow and the down arrow to the right of the value. After the value is entered, select the "Submit" button in order to save the value into the ECM.Adjustment Procedure for Tuning the Exhaust Emissions
Install an emissions analyzer in the exhaust stack after the catalyst.
Operate the engine at a steady state.
Establish communication between Cat ET and the engine Electronic Control Module (ECM). Access the "Service" tab and use the "Service Procedure" "Engine Control System Tuning".
Monitor the following parameters
"Actual Aftertreatment # 1 Intake Oxygen sensor"
"Desired Aftertreatment # 1 Intake Oxygen sensor"
"Actual Aftertreatment # 1 Outlet Oxygen sensor"
"Desired Aftertreatment # 1 Outlet Oxygen sensor"
Determine whether the system is in a rich state or a lean state by monitoring the voltage for both of the actual sensors. A higher voltage corresponds to a rich state and a lower voltage corresponds to a lean state.
Determine whether the actual outlet sensor voltage matches the desired outlet sensor voltage. Allow the voltage to stabilize.
Monitor the emissions analyzer. Verify that the exhaust emissions after the catalyst are within the limit. Refer to the engine Technical Marketing Information (TMI), "Emissions Data".
If the exhaust emissions are not within the acceptable limit,