C6.6 Generator Set Caterpillar

Use this procedure under the following conditions:

Use this procedure if any of the following diagnostic codes are active:

• 100-3 Engine Oil Pressure Sensor voltage above normal

• 100-4 Engine Oil Pressure Sensor voltage below normal

• 100-10 Engine Oil Pressure Sensor abnormal rate of change

• 1785-3 Intake Manifold Pressure Sensor voltage above normal

• 1785-4 Intake Manifold Pressure Sensor voltage below normal

• 1785-10 Intake Manifold Pressure Sensor abnormal rate of change

• 1797-3 Fuel Rail Pressure Sensor voltage above normal

• 1797-4 Fuel Rail Pressure Sensor voltage below normal

The following background information is related to this procedure:

The troubleshooting procedures for the diagnostic codes of each pressure sensor are identical. The 5 Volt sensor supply provides power to all 5 Volt sensors. The Electronic Control Module (ECM) supplies 5.0 ± 0.2 Volts DC to terminal "1" of each sensor connector. The sensor common from the ECM connector goes to terminal "2" 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.

Pull-up Voltage

The ECM continuously outputs a pull-up voltage on the circuit for the sensor signal wire. The ECM uses this pull-up voltage in order to detect an open in the signal circuit. When the ECM detects the presence of a voltage that is above a threshold on the signal circuit, the ECM will generate an open circuit diagnostic code (XXX-3) for the sensor.

If the sensor is disconnected at the sensor connector, the presence of pull-up voltage at the sensor connector indicates that the wires from the sensor connector to the ECM are not open or shorted to ground. If the sensor is disconnected at the sensor connector, the absence of pull-up voltage at the sensor connector indicates an open in the signal wire or a short to ground. If the sensor is disconnected at the sensor connector and the voltage at the sensor connector is different from pull-up voltage, the signal wire is shorted to another wire in the harness.

Illustration 1	g01800518
Typical example of the schematic for the sensors

Illustration 2	g01458448
Typical view of the pin locations on the P2 connector for the pressure sensors (38) Ground (GND) Intake Manifold Pressure Sensor (39) Ground (GND) Oil Pressure Sensor (40) Ground (GND) Fuel Rail Pressure Sensor (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	g01170309
Fuel rail pressure sensor (1) Voltage supply (Vs) (2) Ground (GND) (3) Signal (SIG)

Illustration 4	g01170310
Intake manifold pressure sensor (1) Voltage Supply (Vs) (2) Ground (GND) (3) Signal (SIG)

Illustration 5	g01170311
Typical example of the oil pressure sensor (1) Voltage Supply (Vs) (2) Ground (GND) (3) Signal (SIG)

The troubleshooting procedures for the diagnostic codes of each pressure sensor are identical. The pressure sensors are active sensors. The pressure sensor has three terminals. Active sensors require supply voltage from the ECM. The P2/J2 ECM connector supplies +5 Volts DC to terminal 1 of each sensor. The common line is connected to each sensor connector terminal 2. The signal voltage from terminal 3 of each sensor is supplied to the appropriate terminal at the P2/J2 ECM connector.

Test Step 1. Verify All Active Diagnostic Codes

1. Turn the keyswitch to the ON position. Wait at least 10 seconds for activation of the diagnostic codes.

2. Verify if any of the following diagnostic codes are active:
   • 100-3 Engine Oil Pressure Sensor voltage above normal

   • 100-4 Engine Oil Pressure Sensor voltage below normal

   • 100-10 Engine Oil Pressure Sensor abnormal rate of change

   • 1785-3 Intake Manifold Pressure Sensor voltage above normal

   • 1785-4 Intake Manifold Pressure Sensor voltage below normal

   • 1785-10 Intake Manifold Pressure Sensor abnormal rate of change

   • 1797-3 Fuel Rail Pressure Sensor voltage above normal

   • 1797-4 Fuel Rail Pressure Sensor voltage below normal

Expected Result:

One or more of the preceding diagnostic codes are active.

Results:

• OK - Proceed to Test Step 2.

• Not OK -

  Repair: Do not use this procedure if 1785-10 or 100-10 diagnostic codes are active. Refer to Troubleshooting, "5 Volt Sensor Supply Circuit - Test". When this test is complete, return to the start of this test. If the preceding codes are logged, an intermittent condition may be causing the logged codes. Refer to Troubleshooting, "Electrical Connectors - Inspect".Perform a "Wiggle Test" by using the electronic service tool in order to identify intermittent connections.

  STOP

Test Step 2. Inspect Electrical Connectors And Wiring

1. Thoroughly inspect the terminal connections on the P2/J2 ECM connectors.

2. Thoroughly inspect the following connectors for the engine pressure sensors:
   • P201 Engine Oil Pressure Sensor

   • P228 Fuel Rail Pressure Sensor

   • P200 Intake Manifold Pressure Sensor

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

4. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and the sensor connectors that are associated with the active diagnostic code.

5. Check the screw for the ECM connector for the correct torque of 5 N·m (44 lb in).

6. Check the harness for abrasions and for pinch points from the sensors back to the ECM.

7. Use the electronic service tool to perform a "Wiggle Test". The "Wiggle Test" will identify intermittent connections.

Expected Result:

All connectors, pins, and sockets should be completely coupled and inserted. The harness should be free of corrosion, abrasions and pinch points.

Results:

• OK - Proceed to Test Step 3.

• Not OK -

  Repair: Repair the connectors or the harness and/or replace the connectors or the harness. Ensure that all of the seals are correctly in place and ensure that the connectors are completely coupled.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 3. Verify that the Diagnostic Code is Still Active

1. Turn the keyswitch to the ON position. Wait at least 10 seconds for activation of the diagnostic codes.

2. Use the electronic service tool to check for active diagnostic codes. Record all active diagnostic codes.

3. Determine if the fault is related to an open circuit diagnostic code or a short circuit diagnostic code.

Expected Result:

Either a short circuit diagnostic code is active or an open circuit diagnostic code is active.

Results:

• OK - Short Circuit - A voltage above normal diagnostic code is active at this time. Proceed to Test Step 4.

• OK - Open Circuit - A voltage below normal diagnostic code is active at this time. Proceed to Test Step 5.

• Not OK - A short circuit diagnostic code is not active. An open circuit diagnostic code is not active. An intermittent fault may exist.

  Repair: Use the electronic service tool to perform a "Wiggle Test". If faults are indicated then go to the appropriate procedure.

  STOP

Test Step 4. Disconnect The Sensor In Order To Create An Open Circuit

1. Turn the keyswitch to the OFF position.

2. Disconnect the connector for the sensor with the short circuit diagnostic code.

3. Turn the keyswitch to the ON position. Wait for at least 10 seconds for activation of the diagnostic codes.

4. Use the electronic service tool to check the "Active Diagnostic Code" screen. Check for an open circuit diagnostic code.

Expected Result:

An open circuit diagnostic code for the disconnected sensor is now active.

Results:

• OK - A voltage above normal diagnostic code was active before disconnecting the sensor. An open circuit diagnostic code became active after disconnecting the sensor. Proceed to Test Step 6.

• Not OK - There is a short circuit between the sensor harness connector and the ECM. Leave the sensor disconnected. Proceed to Test Step 8.

Test Step 5. Measure the Sensor Supply Voltage

1. Turn the keyswitch to the OFF position.

2. Disconnect the sensor from the engine harness.

3. Turn the keyswitch to the ON position.

4. Measure the voltage at the plug for the sensor from the terminal 1 (pressure sensor supply) to terminal 2 (sensor common).

Expected Result:

The voltage from terminal 1 to terminal 2 measures 4.84 to 5.16 Volts DC.

Results:

• OK - The sensor supply voltage is correct. Proceed to Test Step 7.

• Not OK - The sensor supply voltage is out of the nominal range. Continue testing the sensor supply circuit.

  Repair: Go to Troubleshooting, "5 Volt Sensor Supply Circuit - Test".

  STOP

Test Step 6. Determine if the Short Circuit is in the Connector or in the Sensor

1. Thoroughly inspect the connector for moisture.

2. Inspect the seals and reconnect the sensor. Refer to Troubleshooting, "Electrical Connectors - Inspect".

4. If the short circuit diagnostic code reappears, the sensor or the sensor connector has a fault.

Expected Result:

The short circuit diagnostic code is still present.

Results:

• OK - There is a fault in the sensor.

  Repair: Perform the following procedure:

  1. Temporarily connect a new sensor to the harness but do not install the new sensor in the engine.

  2. Use the electronic service tool to verify that the replacement sensor eliminates the fault.

  3. If the diagnostic code is eliminated, install the replacement sensor.

  4. Use the electronic service tool to clear the logged diagnostic codes.

  STOP

• Not OK - Repair the engine harness connector. Use the electronic service tool to clear the logged diagnostic codes.
  
  STOP

Test Step 7. Create a Short Circuit Between the Signal and the Common Terminals at the Engine Harness Connector

1. Turn the keyswitch to the ON position.

2. Fabricate a jumper wire that is 150 mm (6 inch) long. Crimp a terminal to both ends of the wire.

3. Monitor the "Active Diagnostic Code" screen of the electronic service tool before installing the jumper wire and after installing the jumper wire.

4. Install the jumper on the engine harness connector. Install one end of the jumper at the sensor signal (terminal 3). Install the other end of the jumper at the common connection for the pressure sensor (terminal 2). Wait at least 30 seconds for activation of the short circuit diagnostic code.

Expected Result:

A short circuit diagnostic code is active when the jumper is installed. An open circuit diagnostic code is active when the jumper is removed.

Results:

• OK - The engine harness and the ECM are OK.

  Repair: Perform the following repair:

  1. Temporarily connect a new sensor to the harness but do not install the new sensor in the engine.

  2. Use the electronic service tool to verify that the replacement sensor eliminates the fault.

  3. If the diagnostic code is eliminated, install the replacement sensor.

  4. Use the electronic service tool to clear the logged diagnostic codes.

  STOP

• Not OK - The open circuit diagnostic code remains active when the jumper is installed. The most probable location for the open circuit is in the common wire for the sensor, or in the sensor signal wire of the engine harness between the ECM and the sensor. Remove the jumper. Proceed to Test Step 8.

Test Step 8. Check the Operation of the ECM by Creating Open and Short Circuits at the ECM Connector

1. Turn the keyswitch to the OFF position.

2. Disconnect the P2 connector from the ECM. Thoroughly inspect both halves of the connector for signs of corrosion or moisture. Refer to Troubleshooting, "Electrical Connectors - Inspect".

3. Reconnect the P2 connector.

4. Turn the keyswitch to the ON position. Use the electronic service tool in order to monitor the "Active Diagnostic Code" screen. Wait at least 10 seconds for activation of the code.

   An open circuit diagnostic code should be active for the suspect sensor.

   Note: When the P2 connector is disconnected, all of the open circuit diagnostic codes for the pressure sensors and temperature sensors will be active. This is normal. Disregard the diagnostic codes for the pressure sensors and the temperature sensors that are not suspect. Address the diagnostic codes for the suspect sensors only.

5. Turn the keyswitch to the OFF position.

6. Fabricate a jumper wire that is 150 mm (6 inch) long. Crimp a terminal to both ends of the wire.

7. Install the jumper wire on the P2 connector. Insert the jumper wire between the terminal for the suspect sensor signal and the common connection for the engine's pressure sensor.

   Use the electronic service tool to verify that there is a short circuit diagnostic code.

Expected Result:

Voltage below normal diagnostic codes and voltage above normal diagnostic codes were active.

Results:

• OK - The ECM is operating correctly. Proceed to Test Step 9.

• Not OK - One of the following conditions exists: The voltage below normal diagnostic code is not active when the harness is disconnected. The voltage above normal diagnostic code is not active when the jumper wire is installed.

  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 at the Caterpillar dealer.

     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. Remove all jumpers and replace all connectors.

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

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

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

  8. 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 9. Bypass the Harness Wiring Between the ECM and the Sensor Connector

1. Turn the keyswitch to the OFF position.

2. Disconnect the P2 connector and disconnect the connector from the suspect sensor.

3. Remove the sensor signal wire from the P2 connector.

4. Remove the signal wire (terminal 3) from the sensor connector on the engine harness.

5. Fabricate a jumper wire that is long enough to reach from the ECM to the sensor connector or use an engine sensor harness bypass with 3 terminals.

   Note: If an engine sensor harness bypass is being made, crimp a socket on one end in order to connect to the ECM. Crimp either a pin or a socket on the other end, as required.

6. Insert the one end of the engine sensor harness bypass into P2 connector on the engine harness. Insert the other end of the engine sensor harness bypass into the sensor connector of the engine harness.

7. Reconnect the P2 connector and the sensor connector.

8. Turn the keyswitch to the ON position.

9. Use the electronic service tool to monitor the "Active Diagnostic Code" screen for either the open circuit diagnostic code for the sensor or the short circuit diagnostic code for the sensor.

Expected Result:

The diagnostic code disappears when the jumper or the bypass is installed.

Results:

• OK - There is a fault in the wiring harness.

  Repair: Perform the following repair:

  1. Repair the faulty harness or replace the faulty harness.

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

  STOP

• Not OK - The most likely cause is an intermittent fault.

  Repair: Use the electronic service tool to perform a "Wiggle Test". If no fault is found, restart this test procedure from Test Step 1.

  STOP