The Electronic Control Module (ECM) monitors the inlet manifold pressure with a sensor. The sensor is located at the front of the engine. A voltage of +5 VDC is supplied to the inlet manifold pressure sensor. The sensor provides a output voltage of 0.4 VDC to 4.4 VDC. This voltage is proportional to the operating pressure range of 0 kPa (0 psi) to 690 kPa (100 psi).
The ECM uses information from the boost pressure sensor to reduce smoke emissions during acceleration. When the ECM senses a higher inlet manifold pressure, the rack limit is increased in order to allow more fuel.
The boost pressure sensor must be calibrated while the engine is off. Calibration is accomplished electronically without the need for manual adjustments. Use Caterpillar Electronic Technician (ET) to recalibrate the sensor. Recalibrate the sensor whenever the ECM or the sensor has been replaced.
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| Illustration 1 | g01635994 |
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| Illustration 2 | g01636024 |
(25) Boost pressure (30) + 5 VDC (35) Analog return | |
| Diagnostic Code | |||
|---|---|---|---|
| Code and Description | Flash Code | Default Conditions which Generate this Code | System Response |
| 102 -00 Boost Pressure Sensor : High | 25 | The boost pressure signal voltage is valid, but above normal. | The diagnostic code is logged. Also, the engine power is limited. boost pressure is set to 600 kPa (87 psi). |
| 102-01 Boost Pressure Sensor : Low | 25 | The boost pressure signal voltage is valid, but below normal. | The diagnostic code is logged. Also, the engine power is limited. boost pressure is set to 600 kPa (87 psi). |
| 102-03 Boost Pressure Sensor : Voltage Above Normal | 25 | The boost pressure signal voltage is greater than 5.0 VDC. | The diagnostic code is logged. Also, the engine power is limited. boost pressure is set to 600 kPa (87 psi). |
| 102-04 Boost Pressure Sensor : Voltage Below Normal | 25 | The boost pressure signal voltage is less than 0.75 VDC. | The diagnostic code is logged. Also, the engine power is limited. boost pressure is set to 600 kPa (87 psi). |
| 102-13 Boost Pressure Sensor : Calibration Required | 42 | The boost pressure sensor is not calibrated. | The fault is active and the ECM converts to low power. Also, boost pressure is set to 0 kPa (0 psi). |
Test Step 1. Inspect Electrical Connectors and Wiring
- Turn the engine control switch to the OFF position.
- Thoroughly inspect the J14/P14 connector, and the J8/P8 connector. Refer to Troubleshooting, "Electrical Connectors - Inspect".
- Perform a 45 N (10 lb) pull test on each of the wires that are associated with the inlet manifold pressure sensor.
- Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect".
- Check the harness for abrasions and for pinch points from the battery to the ECM.
Expected Result:
All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points.
Results:
- OK - All connectors, pins, and sockets are completely coupled and/or inserted. The harness and wiring are free of corrosion, of abrasion, and of pinch points. Proceed to Test Step 2.
- NOT OK - There is a problem in the connectors and/or wiring.
Repair: Repair the connectors or the harness and/or replace the connectors or the harness. Ensure that all of the seals are correctly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.
STOP
Test Step 2. Check for Active Open or Short Diagnostic Codes
- Connect Caterpillar Electronic Technician (ET) to the service tool connector.
- Turn the engine control switch to the ON position.
- Check for active diagnostic codes 102-03 or 102-04.
Expected Result:
No active diagnostic codes exist.
Results:
- OK - No active diagnostic codes exist. Proceed to Test Step 3.
- NOT OK - Diagnostic codes 102-03 or 102-04 are present.
Repair: Refer to Troubleshooting, "Sensor Signal (Analog, Active) - Test.".
STOP
Test Step 3. Calibrate the Boost Sensor
- Connect Cat ET to the Service Tool Connector.
- Turn the engine control switch to the ON position.
- Select the boost sensor calibration screen.
- The calibration will take several seconds.
Expected Result:
The screen will display "Calibrated" when the calibration is complete.
Results:
- OK - The screen displays "Calibrated" when the calibration is complete. Proceed to Test Step 4.
- NOT OK - The screen does not display "Calibrated" when the calibration is complete. Proceed to Test Step 5.
Test Step 4. Boost Pressure Sensor Test
- Remove the sensor from the engine.
- Connect the FT-1906 Air Test Kit to the sensor.
- Connect to the service tool connector.
- Turn the engine control switch to the ON position.
- Close the valve on the test kit and apply 100 kPa (14.5 psi) to the sensor.
- Observe the display on Cat ET.
Note: The leakage rate should not exceed 20 kPa (3 psi) in 30 seconds.
Expected Result:
Cat ET displays 0 ± 20 kPa (0 ± 3 psi) when pressure is not applied. Cat ET displays 100 ± 20 kPa (14.5 ± 3 psi) when pressure is applied.
Results:
- OK - Cat ET displays 0 ± 20 kPa (0 ± 3 psi) when pressure is not applied. Cat ET displays 100 ± 20 kPa (14.5 ± 3 psi) when pressure is applied.
Repair: The boost sensor is working properly. For a intermittent problem, refer to Troubleshooting, "Electrical Connectors - Inspect".
STOP
- NOT OK - Cat ET does not display 0 ± 20 kPa (0 ± 3 psi) when pressure is not applied. Cat ET does not display 100 ± 20 kPa (14.5 ± 3 psi) when pressure is applied. Proceed to Test Step 5.
Test Step 5. Check Supply Voltage at the Sensor
- Turn the engine control switch to the ON position.
- Measure the voltage between P8-A and P8-B.
Expected Result:
The voltage measures 5.0 ± 0.25 VDC.
Results:
- OK - The voltage measures 5.0 ± 0.25 VDC. Proceed to Test Step 7.
- NOT OK - The voltage does not measure 5.0 ± 0.25 VDC. Proceed to Test Step 6.
Test Step 6. Check Supply Voltage at the ECM
- Turn the engine control switch to the ON position.
- Measure the voltage between P14-30 and P14-35.
Expected Result:
The voltage measures 5.0 ± 0.25 VDC.
Results:
- OK - The voltage measures 5.0 ± 0.25 VDC.
Repair: The fault is in the wiring harness. Repair the harness or replace the harness.
STOP
- NOT OK - The voltage does not measure 5.0 ± 0.25 VDC.
Repair: The fault is in the ECM. Replace the ECM.
STOP
Test Step 7. Check Signal Voltage at the Sensor
- Turn the engine control switch to the ON position.
- Measure the voltage between P8-C and P8-B.
Expected Result:
The voltage measurement is between 0.4 VDC and 4.4 VDC.
Results:
- OK - The voltage measurement is between 0.4 VDC and 4.4 VDC. Proceed to Test Step 8.
- NOT OK - The voltage measurement is not between 0.4 VDC and 4.4 VDC.
Repair: Replace the sensor.
STOP
Test Step 8. Check Signal Voltage at the ECM
- Turn the engine control switch to the ON position.
- Measure the voltage between P14-25 andP14-35.
Expected Result:
The voltage measurement is between 0.4 VDC and 4.4 VDC.
Results:
- OK - The voltage measurement is between 0.4 VDC and 4.4 VDC.
Repair: Replace the ECM.
STOP
- NOT OK - The voltage measurement is not between 0.4 VDC and 4.4 VDC.
Repair: The fault is in the wiring harness. Repair the harness or replace the harness.
STOP