The atmospheric pressure sensor provides the ECM with an atmospheric pressure signal. The ECM uses the signal to calibrate the inlet manifold pressure sensor. The information is also used to protect the engine. The ECM limits the fuel rate during high altitude conditions.
| Diagnostic Code | |||
|---|---|---|---|
| Code and Description | Flash Code | Default Conditions which Generate this Code | System Response |
| 106-01 Low Atmospheric Pressure | 26 | The atmospheric pressure is valid, but the pressure is below 0.68 VDC. This is a normal occurrence at altitudes above 1500 m (4921 ft). |
The diagnostic code is logged. Also, the low oil pressure lamp is illuminated. The low atmospheric pressure or the high altitude derate is active. |
| 106-03 Atmospheric Pressure voltage high | 26 | Voltage is above 4.8 VDC for one second. Also, there are no sensor supply diagnostic codes. | The diagnostic code is active and logged. The ECM will use a default value of 100 kPa (14.5 psi). This value will also be displayed on an electronic service tool. |
| 106-04 Atmospheric Pressure voltage low | 26 | The atmospheric pressure signal voltage is less than 0.2 VDC for at least one second. Also, there are no sensor supply diagnostic codes. | The diagnostic code is active and logged. The ECM will use a default value of 100 kPa (14.5 psi). This value will also be displayed on an electronic service tool. |
| 106-10Atmospheric Pressure signal rate of change | 26 | The Atmospheric pressure is changing abnormally. | The diagnostic code is logged if the engine has been running for 15 seconds. |
 | |
| Illustration 1 | g01625935 |
 | |
| Illustration 2 | g01635455 |
(30) +5 VDC (34) Atmospheric pressure (35) Analog return | |
Test Step 1. Inspect the Electrical Connectors and the Wiring Harness
- Remove electrical power from the ECM.
- Thoroughly inspect the connector for the atmospheric pressure sensor and the P15 connector. Inspect the ECM connector J14/P14. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.
- Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the atmospheric pressure sensor.
- Check the allen head screw on the ECM connector for the proper torque. Refer to Troubleshooting, "Electrical Connectors - Inspect" for the correct torque values.
Expected Result:
All connectors, pins, and sockets are completely coupled and/or inserted, and the harness and wiring are free of corrosion, of abrasion and of pinch points.
Results:
- OK - The connectors and wiring are OK. Proceed to Test Step 2.
- Not OK - There is a problem with the connectors and/or the wiring.
Repair: Repair the wiring and connectors or replace the wiring or the connectors. Ensure that all of the seals are properly connected. 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. Refer to Troubleshooting, "Electronic Service Tools".
- Turn the engine control switch to the ON position. The engine should remain off.
- Check for active diagnostic codes 106-03 or 106-04.
Expected Result:
There are no active diagnostic codes.
Results:
- OK - There are no active diagnostic codes. Proceed to Test Step 5.
- Not OK - The service tool shows a short circuit. Proceed to Test Step 4.
- Not OK - The service tool shows a open circuit. Proceed to Test Step 3.
Test Step 3. Check for Opens in the Wiring
- Remove electrical power from the ECM.
- Disconnect the J14/P14 ECM connector and the connector for the atmospheric pressure sensor.
- Measure the resistance between the following terminals:
- P14-30 (ECM connector) to pin J15-A on the connector for the atmospheric pressure sensor
- P14-35 (ECM connector) to pin J15-B on the connector for the atmospheric pressure sensor
- P14-34 (ECM connector) to pin J15-C on the connector for the atmospheric pressure sensor
- P14-30 (ECM connector) to pin J15-A on the connector for the atmospheric pressure sensor
Results:
- OK - The resistance indicates a short circuit. There are no opens in the wiring. Proceed to Test Step 4.
- Not OK - The resistance indicates an open circuit. There is an open circuit or excessive resistance in the harness or the connectors.
Repair: Repair the circuit.Verify that the repair eliminates the problem.
STOP
Test Step 4. Check the Wiring for a Short Circuit
- Measure the resistance between the following terminals:
Note: Wiggle the harness during the following measurements in order to reveal an intermittent condition.
- P14-30 (ECM connector) to pin J15-B and pinP14-30 (ECM connector) to J15-C on the connector for the atmospheric pressure sensor
- P14-35 (ECM connector) to pin J15-C and P14-35 (ECM connector) to pin J15-A on the connector for the atmospheric pressure sensor
- P14-34 (ECM connector) to pin J15-B and P14-34 (ECM connector) to pin J15-A on the connector for the atmospheric pressure sensor
- P14-30 (ECM connector) to pin J15-B and pinP14-30 (ECM connector) to J15-C on the connector for the atmospheric pressure sensor
Expected Result:
Each check of the resistance indicates an open circuit.
Results:
- OK - Each check of the resistance indicates an open circuit. Proceed to Test Step 5.
- Not OK - At least one check of the resistance does not indicate an open circuit. There is a problem in the harness. There may be a problem in a connector.
Repair: Repair the wire and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.
STOP
Test Step 5. Check the Supply Voltage at the Sensor Connector
- Disconnect the atmospheric pressure sensor.
- Restore electrical power to the ECM.
- Measure the voltage between terminals (A) and ( B) at the harness connector for the atmospheric pressure sensor.
 | |
| Illustration 3 | g01356605 |
Harness connector for the atmospheric pressure sensor (A) +5 VDC (B) Return (C) Signal | |
- Remove electrical power from the ECM.
Expected Result:
The voltage measurement is +5.0 ± 0.25 VDC.
Results:
- OK - The voltage measurement is +5.0 ± 0.25 VDC. The supply voltage is reaching the sensor. Proceed to Test Step 7.
- Not OK - The voltage measurement is not +5.0 ± 0.25 VDC. The digital sensor supply voltage is not reaching the sensor. Proceed to Test Step 6.
Test Step 6. Check the +5 Volt Supply Voltage at the ECM
- Remove electrical power from the ECM.
- Disconnect the J14/P14 ECM connector.
- Fabricate a wire jumper that is long enough to be used to measure the supply voltage at the ECM connector. Crimp a connector socket to one end of the wire.
- Remove the wire from terminal location P14-30 (+5 V sensor supply). Install a wire jumper into the socket P14-30.
- Connect the J14/P14 ECM connector.
- Restore electrical power to the engine ECM.
- Measure the voltage between the wire jumper in P14-30 (+5 VDC sensor supply) and engine ground.
- Remove electrical power from the ECM.
- Remove the wire jumper and replace all wires.
Expected Result:
The voltage measurement is +5.0 ± 0.25 VDC.
Results:
- OK - The voltage measurement is +5.0 ± 0.25 VDC. The ECM is operating correctly. Proceed to Test Step 7.
- Not OK - The voltage measurement is not +5.0 ± 0.25 VDC.
Repair: Replace the ECM. Refer to Troubleshooting, "ECM - Replace".
STOP
Test Step 7. Check for Signal Voltage at the Sensor
- Measure the voltage between P15/B and P15/C.
Expected Result:
The measurement should be between 1.6 VDC and 4.8 VDC.
Results:
- OK - The voltage is between 1.6 VDC and 4.8 VDC.
Repair: Check the voltage between P14/35 and P14/34. The voltage should be between 1.6 VDC and 4.8 VDC. Repair the signal wire if the voltage is not present.
STOP
- NOT OK - The voltage is not present between P15/B and P15/C.
Repair: Replace the sensor.
STOP