C6.6 Generator Set Caterpillar

Use this procedure under the following conditions:

This procedure covers open circuit diagnostic codes and short circuit diagnostic codes that are associated with the following sensors:

• Coolant temperature sensor

• Intake manifold air temperature sensor

Use this procedure to troubleshoot the system when one of the following diagnostic codes is active, recently logged or when a diagnostic code can easily be activated.

• 110-3 Engine Coolant Temperature voltage above normal

• 110-4 Engine Coolant Temperature voltage below normal

• 172-3 Intake Manifold Air Temperature voltage above normal

• 172-4 Intake Manifold Air Temperature voltage below normal

The following background information is related to this procedure:

The troubleshooting procedures for the diagnostic codes of each temperature sensor are identical. The temperature sensors are sensors that have two terminals. The connector P2:37 Electronic Control Module (ECM) is the common connection for the engine temperature sensors. The sensor common connection is shared between the temperature sensors. The common line is connected to each sensor connector terminal 2. Terminal 1 is the sensor output. The signal voltage from terminal 1 of each sensor is supplied to the appropriate terminal at ECM Connector P2/J2.

Illustration 1	g01803534
Schematic for engine temperature sensors

Illustration 2	g01803535
Typical view of the P2 pin locations for the pressure sensor (37) Ground (GND) Intake Manifold Air Temperature Sensor (37) Ground (GND) Coolant Temperature Sensor (42) Signal (SIG) Intake Manifold Air Temperature Sensor (43) Signal (SIG) Coolant Temperature Sensor

Illustration 3	g01170313
Engine coolant temperature sensor and intake manifold air temperature sensor (1) Signal (SIG) (2) Ground (GND)

Test Step 1. Verify All Active Diagnostic Codes

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

2. Turn the keyswitch to the ON position.

   Note: Wait at least 30 seconds in order to allow activation of the diagnostic codes.

3. Use the electronic service tool in order to verify if any of the following diagnostic codes are active or recently logged:
   • 110-3 Engine Coolant Temperature voltage above normal

   • 110-4 Engine Coolant Temperature voltage below normal

   • 172-3 Intake Manifold Air Temperature voltage above normal

   • 172-4 Intake Manifold Air Temperature voltage below normal

Expected Result:

One or more of the preceding diagnostic codes are active or recently logged.

Results:

• Yes - Proceed to Test Step 2.

• No - STOP

Test Step 2. Inspect Electrical Connectors And Wiring

1. Thoroughly inspect ECM engine harness connector P2 and the suspect sensor connector. Refer to Troubleshooting, "Electrical Connectors - Inspect".

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

   Refer to illustration 2.

3. Verify that the latch tab of the connector is correctly latched. Also verify that the latch tab of the connector has returned to the fully latching position.

4. Check the screw for the ECM connector for the correct torque of 5.0 N·m (44 lb in).

5. Check the harness for abrasions and for pinch points from the sensor to the ECM.

6. 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/or inserted. The harness should be free of corrosion, abrasion, and pinch points.

Results:

• OK - Proceed to Test Step 3.

• Not OK - 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. Clear all inactive diagnostic codes. Verify that the repair has eliminated the fault. Proceed to Test Step 3 if the fault has not been eliminated.

Test Step 3. Verify That The Diagnostic Code Is Still Active

1. Turn the keyswitch to the ON position.

   Note: Wait at least 30 seconds in order to allow activation of the diagnostic codes.

2. Access the "Active Diagnostic Code" screen on the electronic service tool and check for active diagnostic codes.

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

Expected Result:

A short circuit diagnostic code or an open circuit diagnostic code is active.

Results:

• OK - SHORT Circuit - A short circuit diagnostic code is active at this time. Proceed to Test Step 4.

• OK - OPEN Circuit - An open circuit 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 sensor connector for the sensor with the short circuit diagnostic code.

3. Turn the keyswitch to the ON position.

   Note: Wait at least 30 seconds in order to allow activation of the diagnostic codes.

4. Access the "Active Diagnostic Code" screen on the electronic service tool. Check for an active open circuit diagnostic code.

Expected Result:

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

Results:

• OK - A short circuit diagnostic code was active before disconnecting the sensor. An open circuit diagnostic code became active after disconnecting the sensor.

  Repair: Perform the following procedure:

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

  2. Inspect the seals of the connectors for damage.

  3. Connect the sensor and verify that the fault returns. If the fault returns, the sensor is faulty. Replace the sensor.

  4. Use the electronic service tool to remove all inactive diagnostic fault codes.

  STOP

• Not OK - There is a short circuit between the sensor harness connector and the ECM. Leave the sensor disconnected. Proceed to Test Step 6.

Test Step 5. Create A Short Circuit Between The Signal And The Common Terminals At The Sensor Harness Connector

1. Disconnect the suspect sensor connector P100 for the coolant temperature sensor or disconnect P103 for the inlet manifold temperature sensor.

2. Turn the keyswitch to the ON position.

   Note: Wait at least 30 seconds in order to allow the activation of any diagnostic fault codes.

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

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

5. Install the jumper on the engine harness connector for the suspect sensor, P100 for the coolant temperature sensor and P103 for the intake manifold temperature sensor. Install one end of the jumper at the sensor signal (terminal 1). Install the other end of the jumper at the common connection (terminal 2).

   Note: Wait at least 30 seconds in order to allow 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 the suspect sensor.

  2. If the diagnostic code remains active, replace the sensor.

  3. Verify that the repair eliminates the fault.

  4. Clear all inactive diagnostic codes.

  STOP

• Not OK - The open circuit diagnostic code remains active with the jumper in place. The most probable location for the open circuit is in the sensor common or the sensor signal wire in the engine harness between the ECM and the sensor. Remove the jumper. Proceed to Test Step 6.

Test Step 6. Check The Operation Of The ECM By Creating An Open And A Short Circuit At The ECM Connector

1. Turn the keyswitch to the OFF position.

2. Disconnect the P2/J2 ECM connector.

3. Thoroughly inspect both halves of the connector for signs of corrosion or moisture. Refer to Troubleshooting, "Electrical Connectors - Inspect".

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 30 seconds in order to allow activation of the code.

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

   Note: When P2 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 150 mm (6 inch) long. Crimp a terminal to both ends of the wire.

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

8. Remove the signal pin from the P2 connector for the suspect sensor. Remove the P2:37 connector. Install one end of the jumper at the suspect sensor signal pin on the P2 connector. Install the other end of the jumper toP2:37 common connection for the sensors. Reassemble the P2 connector to the ECM. Use the electronic service tool in order to check the diagnostic codes. Wait at least 30 seconds in order to allow activation of the short circuit diagnostic code.

   Note: The open circuit diagnostic code for the temperature sensor that is not suspect should become active when the sensor common connection is removed from the P2 connector. This code can be disregarded.

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 - Proceed to test step 7.

• Not OK -

  Repair: The ECM does not operate correctly.

  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 7. Bypass The Harness Wiring Between The ECM And The Sensor Connector

1. Turn the keyswitch to the OFF position.

2. Disconnect the P2/J2 connector for the ECM harness, and the suspect sensor connector.

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

4. Remove the signal wire (terminal 1) 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 with sockets on both ends.

6. Insert one end of the jumper into the ECM connector. Insert the other end of the jumper into the sensor connector of the engine harness.

7. Reconnect the connector for the ECM harness and the sensor connector.

8. Turn the keyswitch to the ON position.

9. Use the electronic service tool in order 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 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. Clear all diagnostic codes.

  3. 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 procedure and carefully perform each step.

  STOP