TH48-E80 Petroleum Transmission Power Train Electronic Control System Caterpillar


MID 027 - CID 0826 - FMI 03

Usage:

TH48-E80 FRT
Conditions Which Generate This Code:


Illustration 1g01193071
Schematic of the Temperature Sensor for the Torque Converter Oil

The torque converter oil temperature sensor is located on the torque converter housing.

This diagnostic code is recorded when the ECM reads the signal wire (428-OR(Orange)) of the temperature sensor as being shorted to the +battery circuit. The temperature sensor is a component that produces a PWM output. The sensor signal wire (wire 428-OR(Orange) on the transmission harness and wire F704-OR(Orange) on the ECM harness) connects to connector J2-24 of the ECM connector.

The possible causes of this diagnostic code are listed:

  • A shorted harness

  • A failed sensor

  • An open circuit

  • The ECM may have failed. This is unlikely.

Note: Ensure that the diagnostic code is active.

Note: The following procedure can create numerous related diagnostic codes. Reconnect all harnesses. Then, the related diagnostic codes will be shown as being NOT active. Complete the following procedure. Then, clear all of the related diagnostic codes.

Test Step 1. CHECK THE VOLTAGE AT THE SENSOR.

  1. Turn the disconnect switch and the key start switch to the ON position.

  2. Disconnect the sensor from the machine harness.

  3. At the machine harness connector for the sensor, measure the voltage between contact A (wire 126-PK(Pink)) and contact B (wire J765-BU(Blue)).

Expected Result:

The voltage should measure approximately 24 DCV.

Results:

  • OK - The voltage is approximately 24 DCV. Proceed to test step 4.

  • NOT OK - The voltage is not approximately 24 DCV. There is an open in the machine harness or the ECM has failed. It is unlikely that the ECM has failed. Proceed to test step 2.

Test Step 2. CHECK FOR AN OPEN IN THE SUPPLY CIRCUIT.

  1. The key start switch and the disconnect switch remain in the ON position.

  2. The sensor remains disconnected from the machine harness.

  3. At the machine harness connector for the sensor, measure the voltage from contact A (wire 126-PK(Pink)) to frame ground.

Expected Result:

The voltage measures approximately 24 DCV.

Results:

  • OK - The voltage measures approximately 24 DCV. Proceed to test step 3.

  • NOT OK - The voltage does not measure approximately 24 DCV. The supply circuit is not correct.

    Repair: Repair the circuit or replace the circuit.

    STOP

Test Step 3. CHECK FOR AN OPEN IN THE RETURN CIRCUIT.

  1. Turn the key start switch and the disconnect switch to the OFF position.

  2. The sensor remains disconnected from the machine harness.

  3. Disconnect the machine harness connector J2 from the ECM.

  4. At the machine harness connector for the sensor, install a jumper wire from contact B (wire J765-BU(Blue)) to frame ground.

  5. At the machine harness connector for the ECM, measure the resistance from contact J2-63 (wire J765-BU(Blue)) to frame ground.

Expected Result:

The resistance measurement should measure less than 5 ohms.

Results:

  • OK - The resistance measurement is less than 5 ohms. The harness is correct. The ECM has failed.

    Repair: It is unlikely that the ECM has failed. Recheck the status of the diagnostic code. If the diagnostic code remains present, exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

    STOP

  • NOT OK - The resistance measurement is greater than 5.0 ohms. The resistance that is measured is not correct. There is an open in the harness.

    Repair: The open is in the return circuit with the high resistance measurement. Repair the harness or replace the harness.

    STOP

Test Step 4. CHECK FOR AN OPEN IN THE SIGNAL CIRCUIT.

  1. Turn the key start switch and the disconnect switch to the OFF position.

  2. Disconnect the J2 machine harness connector from the ECM.

  3. At the machine harness connector for the sensor, install a jumper wire from contact C (wire 428-OR(Orange) on the transmission harness and wire F704-OR(Orange) on the ECM harness) to contact B (wire J765-BU(Blue)).

  4. At the machine harness connector J2, measure the resistance from contact J2-24 (wire 428-OR(Orange) on the transmission harness and wire F704-OR(Orange) on the ECM harness) to contact J2-63 (wire J765-BU(Blue)).

Expected Result:

The resistance should measure less than 5 ohms.

Results:

  • OK - The resistance measures less than 5 ohms. Proceed to test step 5.

  • NOT OK - The resistance measurement is greater than 5 ohms.

    Repair: There is an open in the signal circuit. Repair the harness or replace the harness.

    STOP

Test Step 5. CHECK THE SIGNAL WIRE FOR A SHORT TO THE + BATTERY.

  1. The disconnect switch and the key start switch remain in the OFF position.

  2. The machine harness connectors remain disconnected from the ECM.

  3. Remove the jumper wire from contact C (wire 428-OR(Orange) on the transmission harness and wire F704-OR(Orange) on the ECM harness) to contact B (wire J765-BU(Blue)).

  4. At the J1 and J2 machine harness connectors for the ECM, measure the resistance from the signal contact of the sensor J2-24 (wire 428-OR(Orange) on the transmission harness and wire F704-OR(Orange) on the ECM harness) to all possible sources of the +battery circuit.

Expected Result:

Each measurement should be greater than 5.0 ohms.

Results:

  • OK - Each resistance measurement is greater than 5.0 ohms. The sensor has failed.

    Repair: Replace the sensor and verify that the sensor corrected the problem. If the problem persists, exit this procedure and perform this procedure again. If the problem has not been found, replace the ECM. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".

    STOP

  • NOT OK - The resistance measures less than 5.0 ohms. There is short in the machine harness.

    Repair: The short is between the signal circuit and the circuit with the low resistance measurement. Repair the harness or replace the harness.

    STOP

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