C6.6 Generator Set Caterpillar

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

• 262-3 5 Volt Sensor DC Power Supply voltage above normal

• 262-4 5 Volt Sensor DC Power Supply voltage below normal

Also, use this procedure to troubleshoot the system when you have been directed here by another troubleshooting procedure.

The following background information is related to this procedure:

The Electronic Control Module (ECM) supplies regulated +5 Volts DC to the following sensors:

• Fuel Rail Pressure Sensor through connector P228

• Intake Manifold Pressure Sensor through connector P200

• Engine Oil Pressure Sensor through connector P201

The supply for the +5 Volt engine pressure sensor is routed from the ECM through the P2 connector to terminal 1 of each pressure sensor connector. The supply voltage is 5.0 ± 0.16 Volts DC.

The +5 Volt diagnostic code is probably caused by a short circuit to ground or a short circuit to another voltage source in the harness.

A diagnostic code can be caused by the following conditions:

• A short circuit or an open circuit in the harness

• A suspect sensor

• A suspect ECM

Illustration 1	g01800518
Typical example of the schematic for the sensors

Illustration 2	g01800553
Typical example of the locations of the P2 pins for the pressure sensors (38) Ground (GND) Intake Manifold Pressure Sensor (39) Ground (GND) Oil Pressure Sensor (40) Ground (GND) Fuel Rail Pressure Sens (46) Voltage supply (+5 Volts DC) Intake Manifold Pressure Sensor (47) Voltage supply (+5 Volts DC) Oil Pressure Sensor (48) Voltage supply (+5 Volts DC) Fuel Rail Pressure Sensor (51) Signal (SIG) Fuel Rail Pressure Sensor (55) Signal (SIG) Intake Manifold Pressure Sensor (56) Signal (SIG) Oil Pressure Sensor

Illustration 3	g01173224
Typical example of the fuel rail pressure sensor (1) Voltage supply (Vs) (2) Ground (GND) (3) Signal (SIG)

Illustration 4	g01173225
Typical example of the intake manifold pressure sensor (1) Voltage Supply (Vs) (2) Ground (GND) (3) Signal (SIG)

Illustration 5	g01173226
Typical example of the oil pressure sensor (1) Voltage Supply (Vs) (2) Ground (GND) (3) Signal (SIG)

Test Step 1. Check for Connector Damage

1. Turn the keyswitch to the OFF position.

2. Check the connectors and the harness for the following problems:
   • Damage

   • Abrasion

   • Corrosion

   • Incorrect attachment

3. Refer to Troubleshooting, "Electrical Connectors - Inspect".

4. Check the wire connectors at the following positions:
   • ECM

   • Pressure sensors

   The wire connectors are shown in table 1.

5. Check the screws for the ECM connectors for the correct torque of 5.0 N·m (44 lb in).

Expected Result:

The connectors and the harness should be free of the following faults: damage, abrasion, corrosion and incorrect attachment.

Results:

• OK - Proceed to Test Step 2.

• Not OK -

  Repair: Repair the connectors or the harness and/or replace the connectors or the harness.Verify that the repair eliminates the fault.

  STOP

Test Step 2. Check for Active Diagnostic Codes

1. Connect the electronic service tool to the diagnostic connector.

2. Turn the keyswitch to the ON position.

3. Use the electronic service tool in order to monitor the diagnostic codes. Check and record any active diagnostic codes.

   Note: Wait at least 15 seconds in order for the diagnostic codes to become active.

Expected Result:

One of the following diagnostic codes is active:

• 262-3 5 Volt Sensor DC Power Supply voltage above normal

• 262-4 5 Volt Sensor DC Power Supply voltage below normal

Results:

• OK - A 262-4 diagnostic code is active. Proceed to Test Step 3.

• OK - A 262-3 diagnostic code is active. Proceed to Test Step 7.

• Not OK - 262-4 and 262-3 diagnostic codes are not active. Proceed to Test Step 4.

Test Step 3. Disconnect the Sensors

1. Turn the keyswitch to the ON position.

2. Use the electronic service tool in order to monitor the diagnostic codes.

3. Disconnect the pressure sensors one at a time. Wait for 30 seconds after each of the sensors is disconnected.

   Note: The diagnostic code will become inactive when the sensor that caused the diagnostic code is disconnected.

4. Ensure that all the pressure sensors are disconnected.

Expected Result:

The diagnostic code is not active when all of the sensors are disconnected.

Results:

• OK - The diagnostic code is not active when all of the sensors are disconnected.

  Repair: Reconnect all of the sensors except the suspect sensor.

  Proceed to Test Step 4.

• Not OK - The diagnostic code is still active.

  Repair: Leave all of the sensors disconnected.

  Proceed to Test Step 5.

Test Step 4. Install a New Sensor

1. Remove the suspect sensor and connect a replacement sensor. Do not install the replacement sensor to the engine.

2. Use the electronic service tool in order to monitor the diagnostic codes.

Expected Result:

The diagnostic code is not active.

Results:

• OK - The diagnostic code is not active.

  Repair: Install the replacement sensor on the engine. Use the electronic service tool in order to clear all logged diagnostic codes. Replace all wires to the original configuration.Verify that the repair eliminates the fault.

  STOP

• Not OK - The diagnostic code is still active.

  Repair: Do not use the new sensor. Repair the connectors or the wiring and/or replace the connectors or the wiring. Refer to Troubleshooting, "Electrical Connectors - Inspect".Verify that the repair eliminates the fault.

  STOP

Test Step 5. Disconnect the ECM Connector and Check for Active Diagnostic Codes

1. Turn the keyswitch to the OFF position.

2. Connect the electronic service tool to the diagnostic connector.

3. Check the ECM connectors for corrosion and moisture.

4. Disconnect the P2 ECM connector from the ECM.

5. Reconnect the P1 connector to the ECM.

6. Turn the keyswitch to the ON position.

7. Check for active diagnostic codes on the electronic service tool.

   Note: A "voltage high" diagnostic code (open circuit) should be active for all of the following sensors:

   • Engine pressure sensors

   • Engine temperature sensors

Expected Result:

The diagnostic codes are not active. A "voltage high" diagnostic code (open circuit) is active for all of the engine pressure sensors and temperature sensors.

Results:

• OK - The diagnostic code is not active. Proceed to Test Step 6.

• Not OK - The diagnostic codes are still active.

  Repair: Perform the following repair:

  1. Make sure that the latest flash file for the application is installed in the ECM. Refer to Troubleshooting, "Flash Programming".

  2. Contact the Technical Communicator.

     Note: This consultation can greatly reduce the repair time.

  3. If the Technical Communicator recommends the use of a test ECM, install a test ECM. Refer to Troubleshooting, "Replacing the ECM".

  4. Use the electronic service tool to recheck the system for active diagnostic codes.

  5. If the fault is resolved with the test ECM, reconnect the suspect ECM.

  6. If the fault returns with the suspect ECM, replace the ECM.

  7. Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair eliminates the fault.

  STOP

Test Step 6. Check the +5 Volt Supply Wire for a Short to Engine Ground or a Short to Other Wires in the Harness

1. Turn the keyswitch to the OFF position.

2. Disconnect the J2/P2 ECM connector.

3. Ensure that the analog sensors are disconnected at the sensor connectors.

   Note: Wiggle the harness during the following test procedures in order to identify any intermittent short connectors.

4. Measure the resistance from P2:2 to all terminals on the P2 ECM connector. Measure the resistance from the P2:2 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 to engine ground.

  Repair: If a speed control device is installed, repeat this process for J1:54. If the throttle sensors pass the tests, the fault is intermittent.Refer to Troubleshooting, "Electrical Connectors - Inspect".Use the electronic service tool in order to clear all logged diagnostic codes.Replace all wires to the original configuration.Restart the Test Step.

  STOP

• 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 the engine ground.

  Repair: Repair the faulty wire or replace the faulty wire.Use the electronic service tool in order to clear all logged diagnostic codes.Verify that the repair eliminates the fault.

  STOP

Test Step 7. Measure the +5 Volt Supply to the Sensor

1. Turn the keyswitch to the ON position.

   Note: All the pressure sensors should be disconnected.

2. Measure the voltage between terminal 1 (Pressure sensor +5 Volts) and the engine ground for each of the pressure sensors.

Expected Result:

The voltage is 5.0 ± 0.16 Volts DC.

Results:

• OK - The +5 Volt supply is within the expected range. Proceed to Test Step 8.

• Not OK - The voltage is greater than 5.16 Volts DC.

  Repair: Check the +5 Volt supply wire for a short to a higher voltage source.Repair the +5 Volt supply wire and/or replace the +5 Volt supply wire.Verify that the repair eliminates the fault.

  STOP

Test Step 8. Check the Ground Wire

1. Turn the keyswitch to the ON position.

2. Measure the voltage between terminal 1 (pressure sensor +5 Volts) and terminal 2 (pressure sensor ground) on all of the pressure sensors.

3. While the voltage is monitored, perform a 45 N (10 lb) pull test on the ground wires for the +5 Volt supply.

Expected Result:

The voltage is 5.0 ± 0.16 Volts DC.

Results:

• OK - The voltage is within the range.

  Repair: If the fault is intermittent, refer to Troubleshooting, "Electrical Connectors - Inspect".

  STOP

• Not OK - The voltage is not within the range.

  Repair: Inspect the common wire for an open circuit.Repair the common wire and/or replace the common wire.Verify that the repair eliminates the fault.

  STOP