C7 and C9 Marine Engines Caterpillar

Use this procedure to troubleshoot the system when one of the following diagnostic codes is active or easily repeated:

• 262-03 5 Volt Sensor DC Power Supply short to +batt

• 262-04 5 Volt Sensor DC Power Supply short to ground

The Electronic Control Module (ECM) supplies a regulated voltage of 5.0 ± 0.2 VDC to the following sensors:

• Intake air (boost) pressure sensor

• Engine oil pressure sensor

• Fuel pressure sensor

• Injection actuation pressure sensor

• Transmission oil pressure sensor

• Transmission oil temperature sensor

The 5 volt sensor supply provides power to all 5 volt sensors. The ECM supplies 5.0 ± 0.2 VDC to terminal A of each sensor connector. The sensor common from the ECM connector goes to terminal B of each sensor connector. The sensor supply is output short circuit protected. A short circuit to the battery will not damage the circuit inside the ECM.

Note: The sensors are not protected from overvoltage. A short from the supply line to the +Battery may damage the sensors. If the CID-FMI 262-03 is logged, it is possible that all of the sensors have been damaged. Repair the sensor supply and check for any "ACTIVE" sensor diagnostic codes in order to determine if a sensor has failed.

Illustration 1	g01228600
Schematic

Illustration 2	g01180108
Typical location of the engine's 5 volt sensors (1) Fuel pressure sensor (2) Injection actuation pressure sensor (3) Boost pressure sensor (4) Connector for the optional marine transmission oil temperature sensor (5) Connector for the optional marine transmission oil pressure sensor (6) Engine oil pressure sensor (7) J2/P2 ECM connector

Illustration 3	g01149132
P2 terminals that are associated with the 5 volt supply (P2-17) Return (P2-72) +5 VDC (P2-80) +5 VDC (P2-54) Return (P2-81) +5 VDC (P2-93) Return

Test Step 1. Inspect Electrical Connectors and Wiring

1. Remove the electrical power from the ECM.

2. Thoroughly inspect the J1/P1 ECM connector and the J2/P2 ECM connector. Inspect all of the connectors that are associated with the circuit.

   Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".

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

4. Check the ECM connector (allen head screw) for the proper torque. Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect" for details.

5. Check the harness and wiring for abrasion and pinch points from the sensors back to the ECM.

Expected Result:

All connectors, pins and sockets are completely coupled and/or inserted and the harness and wiring are free of corrosion, of abrasion and of pinch points.

Results:

• OK - The harness and connectors appear to be OK. Proceed to Test Step 2.

• Not OK - There is a problem with the connectors and/or wiring.

  Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Ensure that all of the seals are properly in place and ensure that the connectors are completely coupled.Verify that the repair eliminates the problem.

  STOP

Test Step 2. Check for Active Diagnostic Codes

1. Connect the Caterpillar Electronic Technician (ET) to the service tool connector.

2. Restore the electrical power to the ECM.

3. Monitor the active diagnostic code screen on the electronic service tool. Check and record any active diagnostic codes.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

Expected Result:

One of the following diagnostic codes is active:

• 262-03

• 262-04

Results:

• OK - A 03 diagnostic code is active. Proceed to Test Step 4.

• OK - A 04 diagnostic code is active. Proceed to Test Step 3.

• Not OK - No diagnostic code is active.

  Repair: The problem is no longer present. If the problem is intermittent, refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".

  STOP

Test Step 3. Disconnect the +5 V Sensors while you Monitor the Active Diagnostic Codes

1. Monitor the active diagnostic code screen on the electronic service tool. Check and record any active diagnostic codes.

   Note: Wait at least 30 seconds in order for the diagnostic codes to become active.

2. Disconnect the following sensors one at a time and observe Cat ET.
   • Intake air (boost) pressure sensor

   • Engine oil pressure sensor

   • Fuel pressure sensor

   • Transmission oil pressure sensor

   • Transmission oil temperature sensor

3. Wait for 30 seconds after each sensor is disconnected. Check for an active diagnostic code on Cat ET.

Expected Result:

The 04 diagnostic code deactivates.

Results:

• OK - The 04 diagnostic code deactivates. The diagnostic code is not active after a specific sensor is disconnected.

  Repair: Reconnect the sensor that is suspected of causing the problem. If the problem returns after the reconnection of the sensor, disconnect the sensor. If the problem disappears after the disconnection of the sensor, replace the sensor. Reconnect all wires to the original configuration. Clear all diagnostic codes. Verify that the repair eliminates the problem.

  STOP

• Not OK - The 04 diagnostic code stays active. Leave the sensors disconnected. Proceed to Test Step 4.

Test Step 4. Check the +5 V Supply Wire for a Short to Engine Ground or a Short to another Wire in the Harness

1. Remove the electrical power from the ECM.

2. Disconnect the J2/P2 ECM connector.

3. Leave the sensors disconnected at the sensor connectors.

Note: Wiggle the harness during the following measurements in order to reveal any intermittent short condition.

4. Measure the resistance from the ECM connector P2-80 (+5 V Supply) to every terminal on ECM connector P2 and ECM connector P1. Measure the resistance from the ECM connector P2-80 to the ECM ground strap.

5. Measure the resistance from the ECM connector P2-81 (+5 V Supply) to every terminal on ECM connector P2 and ECM connector P1. Measure the resistance from the ECM connector P2-81 to the ECM ground strap.

6. Measure the resistance from the ECM connector P2-72 (+5 V Supply) to every terminal on ECM connector P2 and ECM connector P1. Measure the resistance from the ECM connector P2-72 to the ECM ground strap.

Expected Result:

Each resistance measurement is more than 20,000 Ohms.

Results:

• OK - The resistance check does not indicate a short in the engine harness or a short to engine ground. Proceed to Test Step 5.

• Not OK - A resistance measurement is less than 20,000 Ohms. The +5 V supply wire is shorted in the engine harness or the +5 V supply wire is shorted to engine ground.

  Repair: Repair the wire or replace the wire. Clear all logged diagnostic codes. Reconnect all wires to the original configuration. Verify that the repair eliminates the problem.

  STOP

Test Step 5. Check the +5 V Supply and the Sensor Common for an Open Circuit

1. Install a wire jumper between terminal P2-80 (+5 V Supply) and terminal P2-54 (Sensor Return).

2. Install a wire jumper between terminal P2-81 (+5 V Supply) and terminal P2-93 (Sensor Return).

3. Install a wire jumper between terminal P2-72 (+5 V Supply) and terminal P2-17 (Sensor Return).

Note: Wiggle the harness during the following measurements in order to reveal any intermittent short condition.

4. Record the resistance at each analog sensor connector between terminal A and terminal B.

5. Remove the wire jumpers.

Expected Result:

The resistance is less than 5 Ohms for each measurement.

Results:

• OK - The resistance check does not indicate an open circuit in the engine harness. Proceed to Test Step 6.

• Not OK - A resistance measurement is greater than 5 Ohms. The +5 V supply wire or the sensor return has excessive resistance.

  Repair: Repair the wires or replace the wires. Clear all logged diagnostic codes. Reconnect all wires to the original configuration. Verify that the repair eliminates the problem.

  STOP

Test Step 6. Check the +5 V Supply at the ECM

1. Remove the wire G828-WH from ECM connector P2-72 (+5 V Supply). Install a wire jumper with socket terminals on both ends into P2-72.

2. Remove the 993-BR or G829-GN wire from ECM connector P2-17 (Sensor Return). Install a wire jumper with socket terminals on both ends into P2-17.

3. Remove the wire N940-BU from ECM connector P2-81 (+5 V Supply). Install a wire jumper with socket terminals on both ends into P2-81.

4. Remove the wire N941-YL from ECM connector P2-93 (Sensor Return). Install a wire jumper with socket terminals on both ends into P2-93.

5. Remove the wire G826-BR from ECM connector P2-80 (+5 V Supply). Install a wire jumper with socket terminals on both ends into P2-80.

6. Remove the wire G827-BU from ECM connector P2-54 (Sensor Return). Install a wire jumper with socket terminals on both ends into P2-54.

   Note: Disconnecting the common sensor wire from the ECM will generate an open circuit diagnostic code for all sensors that are connected to the sensor common. Troubleshoot the original diagnostic code. Delete the logged diagnostic codes when you are finished.

7. Reconnect ECM connector J2/P2.

8. Restore the electrical power to the ECM.

9. Measure the voltage between the wire jumper in P2-72 and the wire jumper in P2-17.

10. Measure the voltage between the wire jumper in P2-81 and the wire jumper in P2-93.

11. Measure the voltage between the wire jumper in P2-80 and the wire jumper in P2-54.

12. Remove the electrical power from the ECM.

13. Reconnect all wires to the original configuration.

Expected Result:

The voltage is 5.0 ± 0.2 VDC.

Results:

• OK - The voltage is 5.0 ± 0.2 VDC. The voltage is correct.

  Repair: Clear all diagnostic codes. Check for active diagnostic codes. If the problem is intermittent, refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The voltage is not 5.0 ± 0.2 VDC. The voltage is incorrect.

  Repair: Replace the ECM. Refer to electronic troubleshooting Troubleshooting, "Replacing the ECM".

  STOP