Periodic calibration of the oxygen sensor is required in order to ensure accurate readings and optimum engine performance. Refer to the Operation And Maintenance Manual for the maintenance interval schedule. The engine must be stopped and the sensor must be removed. The sensor must be placed in uncontaminated air in order to calibrate the sensor. The air must be free of exhaust.
During the calibration, the Electronic Control Module (ECM) first establishes the reference for zero percent of oxygen by reading the sensor after the sensor has cooled for two minutes. The ECM energizes the heater in the sensor for five minutes. Last, the ECM reads the percent of oxygen in the surrounding air. The surrounding air is assumed to be clean with approximately 20.95 percent oxygen. The calibration offset and the calibration range are determined from these two points.
Test Step 1. Check for Diagnostic Codes
- Set the engine control to the COOLDOWN/STOP mode.
- Access the "Logged Diagnostic Codes" screen on the Caterpillar Electronic Technician ET. If the following codes are logged, clear the codes:
- 1086-9 Oxygen Sensor Element : Abnormal Update Rate
- 1086-13 Oxygen Sensor Element : Calibration Required
- 1087-3 Oxygen Buffer Module : Voltage Above Normal
- 1087-8 Oxygen Buffer Module : Abnormal Frequency, Pulse Width, or Period
- 1088-5 Oxygen Sensor Power Supply : Current Below Normal
- 1088-6 Oxygen Sensor Power Supply : Current Above Normal
- Access the "Diagnostic Override" screen of Cat ET. Select "Diagnostics/Diagnostic Tests/Override Parameters".
- Turn ON the "Oxygen Sensor Override".
- Allow a minimum of 90 seconds for any diagnostic codes to be generated.
- Access the "Logged Diagnostic Codes" screen again. Look for the following diagnostic codes again: 1086-9, 1086-13, 1087-3, 1087-8, 1088-5 and 1088-6.
Expected Result:
None of the above diagnostic codes are logged.
Results:
- No Codes - The circuit for the oxygen sensor is OK. Proceed to test Step 2.
- Logged 1086-9, 1087-3 or 1087-8 - A 1086-9 1087-3 or 1087-8 diagnostic code is active.
Repair: Refer to Troubleshooting, "Oxygen Sensor Signal".
STOP
- Logged 1088-5 or 1088-6 Diagnostic Code - There is a problem with the supply voltage for the oxygen buffer.
Repair: Refer to Troubleshooting, "Oxygen Sensor Buffer Supply".
STOP
Test Step 2. Calibrate the Oxygen Sensor
- Set the engine control to the OFF/RESET mode.
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During operation, the oxygen sensor may reach temperatures that exceed
700 °C (1292 °F) . Severe personal injury and property damage will result from contact with a hot oxygen sensor.Do not touch the sensor during engine operation, calibration, or testing. Allow the sensor to cool before moving the sensor. Wear gloves that resist heat. Do not place the sensor on or near any flammable material or any surface that can be damaged by high temperatures.
- Disconnect the oxygen sensor from the oxygen buffer.
- Allow the sensor to cool sufficiently for removal. Then remove the sensor from the exhaust system.
- Connect the oxygen sensor to the oxygen buffer. Suspend the sensor in uncontaminated air.
- Set the engine control to the COOLDOWN/STOP mode.
- Access the "Service/Calibrations/Oxygen Sensor" screen of Cat ET. Use Cat ET to start the calibration.
Approximately 12 minutes are required for the calibration.
Expected Result:
Successful calibration is indicated by Cat ET.
Results:
- OK - The calibration was successful. Proceed to Test Step 3.
- Not OK - The calibration was not successful. Cat ET will display a diagnostic code.
Repair: Troubleshoot the diagnostic code. Check the connectors for the oxygen sensor and the oxygen buffer. Repeat the calibration procedure. If the procedure is not successful after three attempts, obtain a new oxygen sensor and repeat the calibration procedure.
STOP
Test Step 3. Verify the Calibration of the Sensor
- Access the "Diagnostic Override" screen of Cat ET. Select "Diagnostics/Diagnostic Tests/Override Parameters".
- Turn ON the "Oxygen Sensor Override" parameter.
Expected Result:
The "Actual Oxygen" reading stabilizes to approximately 20.95 percent in about 30 seconds.
Results:
- OK - The calibration of the oxygen sensor is verified. Allow the sensor to cool before you install the sensor.
STOP
- Not OK - The calibration of the oxygen sensor is not verified.
Repair: Repeat the calibration procedure.
STOP