IT28G Integrated Toolcarrier and 924G, 924GZ and 928G Wheel Loaders Caterpillar

Illustration 1	g02146150
Schematic of the Brake Charging Accumulator pressure sensor

This diagnostic code is associated with the Brake Charging Accumulator pressure sensor for the brake oil. An FMI 03 means the machine ECM has determined the signal output voltage from the oil pressure sensor circuit is above normal.

Possible causes for this diagnostic code are:

• The sensor power supply may have failed.

• The sensor may have failed.

• The sensor output signal may be shorted to a voltage source.

• The sensor output signal may be open.

• The machine ECM may have failed, but is unlikely.

Note: The following test procedure may create other diagnostic codes. Ignore these created diagnostic codes now, but clear those codes after the original diagnostic code has been corrected.

Note:
Poor connections are often the cause of a problem in electrical circuits.
Before performing this procedure, inspect all of the harness connectors involved in the circuit. Verify that all of the connections in the circuit are clean, secure, and in good condition.
If a problem is found with any of the connections: correct the problem and verify that diagnostic code CID 0473 FMI 03 is still active, before performing the following procedures.
Refer to Troubleshooting, "Electrical Connector - Inspect" in this manual.

System Response:

When this diagnostic code occurs, the Brake Oil Diverter solenoid is turned off.

Test Step 1. VERIFY THE +5 DCV SUPPLY.

1. Turn the key start switch and the disconnect switch to the ON position. Do NOT start the engine.

2. Do NOT disconnect any of the machine harness connectors at this time.

3. At the back of the harness connector for the Brake Charging Accumulator presure sensor, insert Multimeter probes along the sensor voltage supply, contact A (R997-OR) and the sensor voltage supply return, contact B (L740-BR).

4. Measure a DC voltage from contact A to contact B.

Expected Result:

The voltage is 5.0 ± 0.5 DCV.

Results:

• YES - The voltage measurement is 5.0 ± 0.5 DCV. The power supply for the sensor is correct. Proceed to Test Step 2.

• NO - The voltage is NOT 5 DCV. The 5 VDC power supply in the machine ECM has failed, or the machine harness has failed. Go to Test Step 3

Test Step 2. CHECK THE SENSOR, THE ECM, AND THE CIRCUIT CONNECTIONS IN THE MACHINE HARNESS.

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

2. Disconnect the machine harness connector from the Brake Charging Accumulator sensor.

3. At the harness connector for the Brake Charging Accumulator sensor, place a jumper wire between the pin for contact C (483-BR ) and the pin for contact B (L740-BR) on the connector.

4. Turn the key start switch and the disconnect switch to the ON position. Do NOT start the engine.

5. Observe the status of the diagnostic code.

Expected Result:

473-03 diagnostic code does not change.

Results:

• YES - The diagnostic code does not change, and remains active. The sensor is NOT the cause of the problem. The machine harness may have failed, or the ECM may have failed. Go to Test Step 3.

• NO - The 473-03 diagnostic code is no longer active. The code has changed into an active 473-03 diagnostic code. The ECM has detected a valid diagnostic code. The ECM, and the harness, are correct. The sensor has failed.

  Repair: Replace the sensor.

  Go to Test Step 5

Test Step 3. CHECK THE SENSOR OUTPUT CIRCUIT FOR AN OPEN.

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

2. If the Brake Charging Accumulator sensor has not been disconnected from the harness connector before this Test Step, disconnect the sensor now.

3. If a jumper wire has not been installed between the pin for contact C (483-BR) and the pin for contact B (L740-BR) on the Brake Charging Accumulator sensor harness connector before this Test Step, install one now.

4. At the machine ECM, disconnect the J1 and J2 machine harness connector from the ECM.

5. At the ECM connector, measure the resistance between contact J1-21 (L740-BR) and contact J1-36 (483-BR).

Expected Result:

The resistance measurement is less than 5 ohms.

Results:

• YES - The resistance measurement is less than 5 ohms. There are no open circuits in the harness. Proceed to Test Step 4.

• NO - The resistance measurement is greater than 5 ohms. The signal circuit is not correct. There is an open or a bad connection in the circuit.

  Repair: Repair, or replace, the machine harness.

  Go to Test Step 5

Test Step 4. CHECK THE SENSOR OUTPUT CIRCUIT FOR A SHORT TO A VOLTAGE SOURCE.

The key start switch and the disconnect switch remain in the OFF position. The machine harness connectors remain disconnected from the machine ECM.

1. The sensor remains disconnected from the harness. Remove the jumper wire installed in a previous step.

2. At the ECM J1 connector, measure the resistance from the sensor signal contact J1-36 (483-BR) to all of the other contacts that are used in the J1 and J2 harness connectors for the ECM.

Expected Result:

Each measurement reads greater than 5000 ohms.

Results:

• YES - Each measurement is greater than 5000 ohms. The signal circuit is not shorted to another circuit. Proceed to Test Step 5.

• NO - One or more of the measurements read less than 5000 ohms. There is a short in the machine harness.

  Repair: The short is between the sensor signal contact (483-BR) and the circuit with the low resistance measurement. Repair, or replace, the harness.

  Go to Test Step 5

Test Step 5. CHECK IF THE DIAGNOSTIC CODE IS STILL ACTIVE.

1. Remove any jumper wires installed during any previous Test Steps.

2. Reconnect all disconnected machine harness connectors. Make sure that all the connectors are fully seated. Observe that the clips for each connector are securely fastened.

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

4. Clear all inactive diagnostic codes.

5. Operate the machine.

6. Check the status of the 473-03 diagnostic code.

Expected Result:

The 473-03 diagnostic code is no longer active.

Results:

• YES - The 473-03 diagnostic code is no longer active. The code does not exist at this time.

  Repair: The cause for the diagnostic code appears to have been corrected. Return the machine back to normal operations.

  STOP

• NO - The 473-03 diagnostic code is still active. The problem has NOT been corrected. The ECM may have failed.

  Repair: If you have not inspected the harness connectors in a previous Test Step, do that now. Refer to Troubleshooting, "Electrical Connector - Inspect" in this manual.Clean the contacts of the harness connectors. Check the wires for damage to the insulation caused by excessive heat, battery acid, or chafing. Perform a 45 N (10 lb.) pull test on each of the wires that are associated with the sensor circuit. Perform a "wiggle test" on the sensor circuit of the machine wiring harness, using the Caterpillar Electronic Technician service tool. The "wiggle test" can be used to detect open or shorted connections in the machine wiring harness. Reconnect all harness connectors. Make sure that the connectors are fully seated. Observe that the clips for each connector are fastened. Perform Test Step 5 again. If the problem has NOT been found, and the original code is still active, the ECM may have failed.
  Prior to replacing an ECM, contact your Dealership Technical Communicator (TC) for possible consultation with Caterpillar, or with the Dealer Solutions Network. This consultation may greatly reduce repair time.
  If the ECM needs to be replaced, see Testing and Adjusting, "Electronic Control Module (ECM) - Replace"in this manual.

  STOP