C7 and C9 Marine Engines Caterpillar

Use this procedure to troubleshoot any suspect problems with the +8 V digital supply.

This procedure covers the following diagnostic codes:

• 263-03 8 Volt DC Supply short to +batt

• 263-04 8 Volt DC Supply short to ground

The digital sensor supply in the Electronic Control Module (ECM) supplies 8.0 ± 0.4 VDC to the throttle position sensor and the coolant level sensor.

A +8 V diagnostic code is probably caused by a short circuit to ground or a short circuit to another voltage source in the harness. The next likely cause is a problem with the sensor. The least likely cause is a problem with the ECM.

Illustration 1	g01149135
Schematic for the 8 volt supply

Test Step 1. Inspect the Electrical Connectors and the Wiring

1. Remove the electrical power from the ECM.

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Illustration 2	g01229023
Typical left side engine view (1) J2/P2 ECM connector

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Illustration 3	g01180117
Typical component locations for the 8 volt supply (2) Coolant level sensor (optional) (3) Exhaust temperature sensor (optional)

2. Thoroughly inspect connector (1). Also, thoroughly inspect each connector for sensors (2) and (3). Refer to the diagnostic functional test Troubleshooting, "Electrical Connectors - Inspect".

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Illustration 4	g01229035
P2 terminals that are associated with the 8 volt supply (P2-92) Return (P2-29) +8 VDC

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Illustration 5	g01159881
Connector for the sensors (A) +8 VDC (B) Return (C) Signal

3. Perform a 45 N (10 lb) pull test on each of the wires in the circuit for the digital sensor supply.

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

5. Check the harness and wiring for abrasions and for pinch points from the sensor 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 connectors and wiring are OK. Proceed to Test Step 2.

• Not OK - There is a problem with the connectors 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.

  STOP

Test Step 2. Check for Active Diagnostic Codes

1. Connect 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 Cat ET. 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:

• 263-03

• 263-04

Results:

• OK - A 03 diagnostic code is active. Proceed to Test Step 3.

• OK - A 04 diagnostic code is active. Proceed to Test Step 4.

• Not OK - No diagnostic code for the digital supply is active. A problem is suspected with a sensor output signal. In order to verify that the sensor is receiving the correct supply voltage, proceed to Test Step 3.

Test Step 3. Check the Voltage on the +8 V Supply Wire

1. Remove the electrical power from the ECM.

2. Disconnect the digital sensors from the sensor connectors.

3. Restore the electrical power to the ECM.

4. Measure the voltage between terminal A and terminal B at each sensor connector.

Expected Result:

The voltage is 8.0 ± 0.4 VDC.

Results:

• OK - The voltage is 8.0 ± 0.4 VDC.

  Repair: Reconnect the sensors. 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 8.0 ± 0.4 VDC. Proceed to Test Step 5.

Test Step 4. Disconnect the +8 V Sensors and Check for an Active Diagnostic Code

1. Monitor the active diagnostic code screen on Cat ET. 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 digital sensors one at a time from the sensor connectors. 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 after a particular sensor is disconnected.

  Repair: Reconnect the sensor. 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. 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 5.

Test Step 5. Check the +8 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 J1/P1 ECM connector and the J2/P2 ECM connector.

3. Leave the digital sensors disconnected.

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

4. Measure the resistance between P2-29 (+8 V digital supply) and every terminal on ECM connector P1 and ECM connector P2.

   1. Measure the resistance between P2-29 (+8 V digital supply) and engine ground.

Expected Result:

Each resistance measurement indicates an open circuit.

Results:

• OK - The resistance measurement does not indicate a short in the engine harness or a short to engine ground. Proceed to Test Step 6.

• Not OK - A resistance measurement does not indicate an open circuit. The +8 V digital supply wire is shorted in the engine harness or the +8 V digital supply wire is shorted to engine ground.

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

  STOP

Test Step 6. Check the +8 V Supply and the Sensor Return for an Open Circuit

1. Install a wire jumper between pin P2-29 (+8 V digital supply) and pin P2-92 (digital return).

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

2. Measure the resistance between terminal A and terminal B at each of the sensor connectors.

3. Remove the wire jumper.

Expected Result:

The resistance is less than ten Ohms for each measurement.

Results:

• OK - The resistance check does not indicate an open circuit in the engine harness. Proceed to Test Step 7.

• Not OK - A resistance measurement is greater than ten Ohms. The +8 V digital supply wire or the sensor common has excessive resistance.

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

  STOP

Test Step 7. Check the +8 V Supply at the ECM

1. Remove the wire R800-OR from ECM connector P2-29 (+8 V digital supply). Install a wire jumper with socket terminals on both ends into P2-29.

2. Remove the wire J842-BK from ECM connector P2-92 (digital return). Install a wire jumper with socket terminals on both ends into P2-92.

3. Reconnect ECM connector J1/P1 and J2/P2.

4. Restore the electrical power to the ECM.

5. Measure the voltage between the wire jumper in P2-29 and the wire jumper in P2-92.

6. Remove the electrical power from the ECM.

7. Reconnect all wires to the original configuration.

Expected Result:

The voltage is 8.0 ± 0.4 VDC.

Results:

• OK - The voltage is 8.0 ± 0.4 VDC.

  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 8.0 ± 0.4 VDC.

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

  STOP