The Electronic Control Module (ECM) attempts to perform an automatic calibration of all pressure sensors whenever the ECM is powered and the engine is OFF for at least five seconds. Cranking the engine during the first five seconds causes the ECM to abort the calibration attempt. Perform a manual calibration if a pressure sensor is replaced.
During an automatic pressure sensor calibration, the ECM checks all pressure sensors against an acceptable range. If any pressure sensor reading is outside the acceptable range, the previous calibration value is used. The ECM then calibrates all pressure sensors against the atmospheric pressure sensor.
During a manual pressure sensor calibration, the ECM checks the signal from the atmospheric pressure sensor against an acceptable range of pressures. The ECM then calibrates the remaining analog pressure sensors against the atmospheric pressure sensor. The ECM also uses an offset value to calibrate the remaining analog sensors. A diagnostic code with an FMI - 13 "Calibration Required" is generated if the value of the offset is not within an acceptable range.
A pressure sensor calibration will not be successful if there are any active diagnostic codes for pressure sensors with an FMI - 03 "open/short to +batt" or an FMI - 04 "short to ground".
Test Step 1. Check for Active Diagnostic Codes
- Turn the keyswitch to the OFF/RESET position.
- Connect the Caterpillar Electronic Technician (Cat ET) to the data link connector.
- Turn the keyswitch to the ON position.
- Check for active diagnostic codes.
Expected Result:
There are no active diagnostic codes.
Results:
- OK - Proceed to Test Step 2.
- Not OK - A pressure sensor with an active diagnostic code cannot be calibrated.
Repair: Perform the appropriate troubleshooting procedure for the active diagnostic code.
Repeat Test Step 1.
Test Step 2. Perform a Manual Calibration of the Sensors
- Select "Calibrate Pressure Sensors" on Cat ET. The ECM will perform a manual pressure sensor calibration when this screen is entered.
Expected Result:
Cat ET indicates that the calibration was completed.
Results:
- OK - Cat ET indicates that the calibration was completed.STOP
- Not OK - All pressure sensors could not be calibrated. Proceed to Test Step 3.
Test Step 3. Determine the Cause of the Failed Manual Calibration
- Check if any pressure sensors have FMI - 13 "calibration required" in order to determine the sensor that is not functioning correctly.
- Verify that the correct sensor has been installed.
- Check the "Status" screen on Cat ET for the pressure sensor reading.
- Turn the keyswitch to the OFF/RESET position.
- Record the barometric pressure in your area from a valid source.
Expected Result:
Offset values:
- The turbocharger compressor inlet pressure does not differ from atmospheric pressure by more than 8 kPa (1.1 psi).
- The turbocharger outlet pressure does not differ from atmospheric pressure by more than 15 kPa (2.0 psi).
- The engine oil pressure does not differ from atmospheric pressure by more than 27 kPa (4.0 psi).
- The atmospheric pressure does not differ from actual barometric pressure by more than 5 kPa (0.7 psi).
Results:
- OK - Repeat manual calibration of the sensors.STOP
- Not OK - There is a problem with the wiring harness and/or the sensor. Inspect the components for damage, corrosion, and abrasion. Repair the components and/or replace the components. Repeat Test Step 1.