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| Illustration 1 | g02646653 |
Schematic for the Sensor Power Supply | |
Note: THE HARNESS BETWEEN THE ECM AND THE OEM CONNECTOR IS NOT A CATERPILLAR HARNESS. FOR MORE INFORMATION ABOUT THIS HARNESS PLEASE CONTACT THE OEM MANUFACTURER.
This diagnostic code is recorded when the ECM reads the voltage of the sensor supply circuit (R977-OR) as above normal range.
The possible causes of this diagnostic code are listed below:
- The supply circuit (R977-OR) to the sensors is shorted to the +battery.
- The 5V power supply of the Charge Pressure sensor has failed.
- The ECM has failed. An ECM failing is unlikely.
Test Step 1. CHECK THE SUPPLY CIRCUIT FOR A SHORT TO THE + BATTERY.
- Turn the Disconnect switch and the key start switch to the OFF position.
- Disconnect the machine harness from the charge pressure sensor.
- At machine harness connector charge pressure sensor, measure the resistance from Pin A (R997-OR) to Pin B (J764-BR).
Expected Result:
The resistance should be greater than 5000 ohms for each measurement.
Results:
- OK - The resistance is greater than 5000 ohms for each measurement. The machine harness is correct. Proceed to Test Step 3.
- NOT OK - The resistance is not greater than 5000 ohms for each measurement.
Repair: The Sensor Power circuit is shorted to +B. Repair the machine harness or replace the machine harness.
STOP
Test Step 2. CHECK FOR POWER FROM THE CHARGE PRESSURE SENSOR
- Reconnect the connector for the machine harness to the charge pressure sensor.
- Turn the Disconnect switch and Key switch to the ON position.
- Insert a multimeter probe at the back of the connector for the charge pressure sensor at Pin A (Wire R997-OR).
- Insert the other multimeter probe at the back of the connector for the charge pressure sensor at Pin B (Wire J764-BR).
- Measure the voltage from Pin A (Wire A916-OR) to Pin B (Wire J764-BR).
Expected Result:
The voltage measures 4.85 - 5.15 VDC.
Results:
- OK - The voltage measures 4.85 - 5.15 VDC. Proceed to Test Step 3.
- NOT OK - The voltage does NOT measure 4.85 - 5.15 VDC. The charge pressure sensor may have failed.
Repair: Prior to replacing the charge pressure sensor, contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. If the charge pressure sensor is to be replaced.
STOP
Test Step 3. CHECK IF THE DIAGNOSTIC CODE IS STILL ACTIVE.
- Inspect the harness connectors. Clean the contacts of the harness connectors. Check the wires for damage to the insulation that is caused by excessive heat, corrosion, or chafing.
- Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit.
- Reconnect all harness connectors making sure that the connectors are fully seated and the clips for each connector are fastened.
- Turn the disconnect switch and the key start switch to the ON position.
- Use the Caterpillar Electronic Technician (ET) service tool, if available, in order to perform a "Wiggle Test" on the machine wiring harness. The wiggle test can detect intermittent shorts or opens in the machine wiring harness.
- Operate the machine.
- Determine if the SPN 1542 FMI 03 diagnostic code is active.
Expected Result:
The SPN 1542 FMI 03 is active.
Results:
- YES - The SPN 1542 FMI 03 is active. The problem has not been corrected.
Repair: Check the circuit again. If the Caterpillar Electronic Technician (ET) is available, use the Cat ET service tool in order to perform a "Wiggle Test" on the machine wiring harness. The "Wiggle Test" can detect shorts and opens in the machine wiring harness that are momentary or intermittent.An ECM failure is unlikely. Exit this procedure and perform this procedure again. If the cause of the diagnostic code is not found, replace the ECM. Prior to replacing an ECM, always contact your dealership for possible consultation with Caterpillar. This consultation may greatly reduce repair time. See Testing and Adjusting, "Electronic Control Module (ECM) - Replace".
STOP
- NO - The SPN 1542 FMI 03 is not active. The problem does not exist at this time.
Repair: The initial diagnostic 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 machine operation.
STOP