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| Illustration 1 | g01294799 |
Connections for the fuel level sensor | |
This diagnostic code is recorded when the IQAN-XT2 module reads the signal voltage of the fuel level sender and the voltage is too low. The following problems could signal this diagnostic code:
- The sender has failed.
- The ground circuit for the sender is open in the machine harness.
- The signal circuit in the machine harness is open or the sender is disconnected.
- The module has failed. This is unlikely.
Note: This circuit contains a 390 Ω resistor. The connections, the continuity, and the resistance value of this resistor should all be checked. The resistor is located in front of the swing motor between the tower plates of the upper frame on TK711 through TK732 machines. The resistor is located near the pilot manifold on the bottom side of TK741 through TK752 machines. The bottom cover plate must be removed in order to access the resistor on these machines.
System Response:
This failure causes the fuel gauge to always indicate an empty fuel tank or the fuel gauge may intermittently indicate an empty fuel tank.
Test Step 1. CHECK THE RESISTANCE OF THE SENDER
- Turn the disconnect switch and the key start switch to the OFF position.
- Disconnect the machine harness connector from the fuel level sender.
- At the connector for the sender, measure the resistance between the contact 1 and the contact 2.
Expected Result:
The resistance measurement should be between approximately 98 ohms when the tanks is empty and approximately 0 ohms when the tank is full. When the tank has some fuel, the resistance of the sender should be between the 0 ohm and the 98 ohm range.
Results:
- OK - The resistance measurement is between the correct range. The sender is OK. Proceed to Test Step 3
- NOT OK - The resistance measurement is not between the correct range. The sender is faulty.
Repair: Replace the fuel level sender. Ensure that the new sender corrects the problem.
STOP
Test Step 2. CHECK THE RETURN CIRCUIT OF THE HARNESS
The sender remains disconnected from the machine harness. The disconnect switch and the key start switch remain in the OFF position.
- Disconnect the machine harness connector from the IQAN-XT2 module.
- Measure the resistance of the return circuit between contact 2 (wire 975-WH) of the machine harness for the sender and contact IQAN XT2 A0 - 13 (wire 975-WH) of the machine harness for the module.
Expected Result:
The resistance is less than 5 ohms.
Results:
- OK - The resistance is less than 5.0 ohms. The harness resistance is correct. Proceed to Test Step 3.
- NOT OK - The resistance is greater than 5.0 ohms. The ground circuit in the harness has failed. There is an open circuit or a bad connection in the ground circuit for the sender.
Repair: Refer to the complete machine Electrical System Schematic. Ensure that all connections and splices in the ground circuit for the sender are clean, secure and in good condition. Repair the machine harness or replace the machine harness.
STOP
Test Step 3. CHECK THE SIGNAL CIRCUIT OF THE HARNESS
The sender remains disconnected from the machine harness. The disconnect switch and the key start switch remain in the OFF position.
- At the machine harness connector for the sender, measure the resistance of the signal circuit between contact 1 (wire 447-PK) and contact IQAN XT2 A0 - 36 (wire 447-PK) of the machine harness for the module.
Expected Result:
The resistance is less than 5 ohms.
Results:
- OK - The resistance is less than 5.0 ohms. The harness resistance is correct. Proceed to Test Step 4.
- NOT OK - The resistance is greater than 5.0 ohms. The signal circuit in the harness has failed. There is an open circuit or a bad connection in the signal circuit for the sender.
Repair: Refer to the complete machine Electrical System Schematic. Ensure that all connections and in the signal circuit for the sender are clean, secure and in good condition. Repair the machine harness or replace the machine harness.
STOP
Test Step 4. CHECK THE STATUS OF THE DIAGNOSTIC CODE
- Inspect the harness connectors on the sensor, the resistor, and the module and clean the contacts of the machine harness connectors.
- Reconnect all disconnected harness connectors.
- Turn the disconnect switch and the key start switch to the ON position.
- Operate the machine.
- Check the status of the Input low error diagnostic code for pin 36 of the IQAN-XT2 module.
Expected Result:
The Input low error diagnostic code for pin 36 of the IQAN-XT2 module is not active.
Results:
- OK - The Input low error diagnostic code for pin 36 of the IQAN-XT2 module is not active. The diagnostic code does not exist at this time. The initial diagnostic code was probably caused by a poor connection or a short at one of the connectors that was disconnected and reconnected. Resume normal operation.STOP
- NOT OK - The Input low error diagnostic code for pin 36 of the IQAN-XT2 module is active. The diagnostic code has not been corrected. The module may have failed.
Repair: If the cause can not be found, the module may have failed. Prior to replacing a module, always contact your dealership's Technical Communicator for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the cause of the diagnostic code is not found, replace the IQAN-XT2 module.
STOP