CX28 Transmission For Combat and Tactical Vehicles Transmission ; Transfer Case Electronic Control System Caterpillar

Illustration 1	g01249620
Schematic of the 5 V sensor supply

The 5 V power supply provides power to the oil level sensor for the transmission.

The SPN 3509 FMI 3 diagnostic trouble code is recorded when the ECU reads the voltage of the sensor supply circuit as higher than the normal voltage.

The following is a list of possible causes for this diagnostic trouble code:

• The sensor supply circuit is shorted to the +battery circuit.

• The return circuit is open in the machine harness.

• A sensor has failed.

• The ECU has failed. This is unlikely.

Note: The following test procedure may create other diagnostic trouble codes. Ignore these created diagnostic trouble codes and clear these diagnostic trouble codes when the original diagnostic trouble code has been corrected. Ensure that the diagnostic trouble code of SPN 3509 FMI 3 is active before performing this procedure.

Note: Use a digital multimeter for the measurements in this procedure.

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 machine harness connector from the sensor.

3. At the machine harness connector for the sensor, measure the voltage from connector contact 1 (wire 709-OR) to connector contact 2 (wire 202-BK). Measure the voltage from connector contact 1 (wire 709-OR) to frame ground.

Expected Result:

Both voltage measurements are 5.0 ± 0.5 DCV.

Results:

• OK - Both voltage measurements are 5.0 ± 0.5 DCV. The voltage is correct. Proceed to Test Step 3.

• NOT OK - The voltage measurement from connector contact 1 (wire 709-OR) to the frame ground is 5.0 ± 0.5 DCV. However, the voltage measurement from connector contact 1 to connector contact 2 is not 5.0 ± 0.5 DCV. The return circuit is faulty in the machine harness.

  Repair: The return circuit is faulty in the machine harness. Refer to the complete Electrical System Schematic for the vehicle that is being serviced. Examine all connection points in the return circuit for the sensor. Ensure that all connections are clean and secure. Make sure that the connections are in good condition. Repair the machine harness or replace the machine harness.

  STOP

• NOT OK - Both of the voltage measurements are greater than 5.0 ± 0.5 DCV. There may be a short in the machine harness. Proceed to Test Step 2.

Test Step 2. CHECK THE HARNESS FOR A SHORT TO THE +BATTERY

The machine harness connector remains disconnected from the sensor.

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

2. Disconnect the machine harness connectors J1 and J2 from the ECU.

3. At the harness connector J1, check the resistance from contact J1-11 (wire 709-OR) to all of the other +battery contacts that are connected to the ECU.

Expected Result:

Each resistance measurement is greater than 5000 ohms.

Results:

• OK - Each resistance measurement is greater than 5000 ohms. The supply circuit is not shorted to a +battery circuit. Proceed to Test Step 3.

• NOT OK - One or more of the resistance measurements is less than 5000 ohms. There is a short in the machine harness.

  Repair: The power supply circuit is shorted to a +battery circuit in the machine harness. Refer to the complete Electrical System Schematic for the vehicle that is being serviced. Examine the supply circuit in order to determine the location of the problem. Repair the machine harness or replace the machine harness.

  STOP

Test Step 3. CHECK IF THE DIAGNOSTIC TROUBLE CODE IS STILL ACTIVE.

1. Inspect the harness connectors. Clean the contacts of the harness connectors and check the wires for damage to the insulation that is caused by excessive heat, battery acid, or chafing.

2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit.

3. Reconnect all harness connectors in order to make sure that the connectors are fully seated. Also, make sure that the clips for each connector are completely fastened.

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

5. Operate the vehicle.

6. Determine if the SPN 3509 FMI 3 diagnostic trouble code is active.

Expected Result:

The SPN 3509 FMI 3 diagnostic trouble code is active.

Results:

• YES - The SPN 3509 FMI 3 diagnostic trouble code is active. The problem has not been corrected. The sensor may have failed or the ECU may have failed.

  Repair: Replace the pressure sensor. Replace the pressure sensor. After the sensor is replaced, perform this test again. It is unlikely that the ECU has failed. Exit this procedure and perform this procedure again. If the cause of the diagnostic trouble code is not found, replace the ECU. Prior to replacing an ECU, always contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. See Testing and Adjusting, "Electronic Control Unit - Replace".

  STOP

• NO - The SPN 3509 FMI 3 diagnostic trouble code is not active. The problem does not exist at this time. The initial diagnostic trouble code was probably caused by a poor electrical connection or a short at one of the harness connectors that was disconnected and reconnected. Resume normal vehicle operation.STOP