3412E Petroleum Engine Auxiliary Temperature Sensor Circuit - Test Caterpillar


Auxiliary Temperature Sensor Circuit - Test
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System Operation Description:

Use this procedure to troubleshoot any suspect problems with the auxiliary temperature sensor.

Use this procedure to troubleshoot the following diagnostic codes:

  • 1836-03 Auxiliary Temperature Sensor open/short to +batt

  • 1836-04 Auxiliary Temperature Sensor short to ground

The auxiliary temperature sensor receives a regulated voltage supply of 8.0 ± 0.4 VDC from the Electronic Control Module (ECM).

Note: Refer to the diagnostic functional test Troubleshooting, "Digital Sensor Supply Circuit - Test" if the ECM has detected a problem with the digital sensor supply voltage.

Note: The circuit for the auxiliary temperature sensor utilizes a resistor assembly that is wired in parallel across the signal wire and the return wire. The resistor is used to condition the pulse width modulated signal for the ECM. If the resistor is not present in the circuit then diagnostic codes for the sensor will become active. The resistor is installed in the harness between the customer connector and the sensor connector.




Illustration 1g01136421

Schematic for auxiliary temperature sensor

------ WARNING! ------

The connection of any electrical equipment and the disconnection of any electrical equipment may cause an explosion hazard which may result in injury or death. Do not connect any electrical equipment or disconnect any electrical equipment in an explosive atmosphere.

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Test Step 1. Verify that the Auxiliary Temperature Sensor is Installed

  1. Locate the auxiliary temperature sensor. Verify that a auxiliary temperature sensor is installed.

  1. Connect Cat ET to the service tool connector. Check the "Auxiliary Temperature Sensor" parameter on the configuration screen.

Expected Result:

An auxiliary temperature sensor is installed on the application and the "Auxiliary Temperature Sensor" parameter is programmed to a value of "1" to "120" in Cat ET.

Results:

  • OK - The auxiliary temperature sensor is properly installed. Proceed to Test Step 2.

  • Not OK - The auxiliary temperature sensor is not installed on the application.

    Repair: Change the "Auxiliary Temperature Sensor" parameter to "0", or install the sensor. Verify that the repair eliminates the problem.

    STOP

  • Not OK - The "Auxiliary Temperature Sensor" parameter is improperly programmed.

    Repair: Use Cat ET to program the "Auxiliary Temperature Sensor" parameter to a value of "1" to "120". Verify that the repair eliminates the problem.

    STOP

Test Step 2. Inspect the Electrical Connectors and the Wiring

  1. Turn the keyswitch to the OFF position.



    Illustration 2g01136484

    Top view

    (1) P1 ECM connector

    (2) P2 ECM connnector

    (3) P3 Customer connetor

  1. Thoroughly inspect connectors (1), (2), and (3). Also inspect the connector for the auxiliary temperature sensor. Refer to Troubleshooting, "Electrical Connectors - Inspect".



    Illustration 3g01136422

    ECM P1 connector

    (P1-35) +8 V Supply

    (P1-29) Return




    Illustration 4g01136469

    ECM P2 connector

    (P2-25) Auxiliary temperature sensor




    Illustration 5g01136423

    J3 and P3 connectors

    (8) +8 V supply

    (9) Return

    (11) Auxiliary temperature sensor

  1. Perform a 45 N (10 lb) pull test on each of the wires that is associated with the auxiliary temperature sensor circuit.

  1. Check the torque of the allen head screws for the ECM connectors and for the customer connector. 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 in good repair. Proceed to Test Step 3.

  • Not OK - There is a problem with the connectors and/or wiring.

    Repair: Repair the wiring and connectors or replace the wiring and the connectors. Ensure that the seals are correctly installed on each of the connectors. Verify that the repair eliminates the problem.

    STOP

Test Step 3. Check the Sensor Supply Voltage at the Sensor Connector

  1. Disconnect the J114/P114 auxiliary temperature sensor connector.

  1. Turn the keyswitch to the ON position.

  1. Use a multimeter to measure the voltage between terminal A (+8 V digital supply) and terminal B (sensor return) at the harness connector for the auxiliary temperature sensor.

  1. Turn the keyswitch to the OFF position. Connect the J114/P114 auxiliary temperature sensor connector.

Expected Result:

The digital sensor supply voltage between A +8 V digital supply and B sensor return is 8.0 ± 0.4 VDC.

Results:

  • OK - The supply voltage is reaching the sensor. Proceed to Test Step 4.

  • Not OK - The digital sensor supply voltage is not reaching the sensor.

    Repair: Refer to the diagnostic functional test Troubleshooting, "Digital Sensor Supply Circuit - Test" for the appropriate troubleshooting procedure.

    STOP

Test Step 4. Check for Active Diagnostic Codes

  1. Turn the keyswitch to the ON position.

  1. Monitor the active diagnostic code screen on Cat ET. Check and record any active diagnostic codes.

    Note: Wait at least 15 seconds in order for the diagnostic codes to become active.

Expected Result:

No diagnostic codes are active.

Results:

  • OK - No diagnostic codes are active.

    Repair: The problem may have been related to a faulty connection in the harness. Carefully reinspect the connectors and wiring. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".

    STOP

  • Active 1836-04 code - A 1836-04 diagnostic code is active. Proceed to Test Step 5.

  • Active 1836-03 code - A 1836-03 diagnostic code is active. Proceed to Test Step 6.

Test Step 5. Check for a Short in the Signal Wire

  1. Disconnect the following connectors.

    • P114/J114 auxiliary temperature sensor connectors

    • J1/P1 ECM connectors

    • J2/P2 ECM connectors

  1. Measure the resistance between terminal P2-25 (auxiliary temperature sensor signal) and every terminal on the P1 and P2 connectors.

    Wiggle the harness during each measurement in order to locate any opens or shorts in the harness.

  1. Measure the resistance between the suspect sensor's signal wire and engine ground.

Expected Result:

Each check indicated an open circuit.

Results:

  • OK - Each check of the resistance indicated an open circuit. Proceed to Test Step 6.

  • Not OK - The signal wire is shorted somewhere in the harness.

    Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Verify that the repair eliminates the problem.

    STOP

Test Step 6. Check for an Open in the Signal Wire

  1. Measure the resistance between P2-25 auxiliary temperature sensor signal and terminal "C" on the harness connector for the auxiliary temperature sensor.

    Wiggle the harness during the measurement in order to locate any opens or shorts in the harness.

Expected Result:

The resistance is less than five Ohms.

Results:

  • OK - The resistance is less than five Ohms. There is not an open in the signal wire. Proceed to Test Step 7.

  • Not OK - The resistance is more than five Ohms. There is an open circuit or excessive resistance in the signal wire.

    Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Verify that the repair eliminates the problem.

    STOP

Test Step 7. Check the Resistance of the Harness

  1. Install a jumper wire between terminals P114-B (auxiliary temperature sensor return) and P114-C (auxiliary temperature sensor signal).

  1. Measure the resistance between terminals P1-68 (auxiliary temperature sensor signal) and P1-5 (auxiliary temperature sensor return) at the ECM connector.

    The correct resistance for the circuit is 1700 Ohms to 1900 Ohms.

Expected Result:

The resistance measurement for the circuit is within specifications.

Results:

  • OK - The resistance measurement is within specifications. Remove the jumper wire. Connect the J1/P1 and the J2/P2 ECM Connectors. Proceed to Test Step 8.

  • Not OK - The resistance measurement is not within specifications.

    Repair: Locate the resistor in the sensor harness. Replace the resistor. Ensure that the wire splice that is used for the installation of the wiring for the resistor is providing a good connection. Verify that the repair eliminates the problem.

    STOP

Test Step 8. Check the Digital Sensor's Signal Frequency and the Duty Cycle at the Sensor Connector

  1. Turn the keyswitch to the OFF position.

  1. Install a breakout T between J114 and P114 at the sensor connector.

  1. Connect the auxiliary temperature sensor.

  1. Turn the keyswitch to the ON position.

  1. Measure the frequency and the duty cycle between terminal C (auxiliary temperature sensor signal) and terminal B (auxiliary temperature sensor return) of the breakout T.

    Wiggle the harness during the measurement in order to locate any opens or shorts in the harness.

  1. Turn the keyswitch to the OFF position.

  1. Remove the breakout T. Connect the sensor connector.

Expected Result:

The frequency reading is 500 ± 200 Hz. The duty cycle is between 10 percent to 89 percent.

Results:

  • OK - The frequency and the duty cycle are correct. Proceed to Test Step 9.

  • Not OK - The frequency and the duty cycle are not correct.

    Repair: Replace the sensor. Verify that the problem is resolved.

    STOP

Test Step 9. Check the Digital Sensor's Signal Frequency and the Duty Cycle at the ECM

  1. Turn the keyswitch to the OFF position.

  1. Install a breakout T between J2 and P2 ECM connectors. Install a breakout T between J1 and P1 ECM connectors.

  1. Turn the keyswitch to the ON position.

  1. Measure the frequency and the duty cycle between P1-29 digital sensor return and P2-25 auxiliary temperature sensor of the breakout harness.

    Wiggle the harness during the measurement in order to locate any opens or shorts in the harness.

  1. Turn the keyswitch to the OFF position.

  1. Remove the breakout harnesses. Connect both ECM connectors.

Expected Result:

The frequency reading is 500 ± 200 Hz. The duty cycle is between 10 percent to 89 percent.

Results:

  • OK - The frequency and the duty cycle are correct.

    Repair: Verify that the diagnostic code is still active. If the diagnostic code is still active and the wire for the signal is OK, replace the ECM. Refer to Troubleshooting, "Replacing the ECM".Verify that the repair eliminates the problem.

    STOP

  • Not OK - The frequency and the duty cycle are not correct. The problem is in the J1/P1 ECM connectors.

    Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Verify that the repair eliminates the original problem.

    STOP

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