3176C, 3406E and 3456 Industrial Engines Troubleshooting – Injector Solenoid – Test

System Operation Description:

Use this procedure to troubleshoot the electrical system if a problem is suspected with the injectors or if any one of the diagnostic codes in Table 1 is active or easily repeated.

Table 1
Diagnostic Codes Table
Code and Description Conditions which Generate this Code System Response
1-5 Cylinder #1 : Injector current below normal The Electronic Control Module (ECM) detects an open circuit. The code is logged.
The ECM continues to fire the injector solenoid.
1-6 Cylinder #1 Injector : Current Above Normal The ECM detects a short circuit. The code is logged.
The ECM will disable the solenoid circuit. The ECM will periodically try to fire the injector. If the short circuit remains, this sequence of events will be repeated until the problem is corrected.
1-11 Cylinder #1 Injector : Other Failure Mode The ECM detects a problem in the circuit for the injector. The code is logged.
The ECM will periodically try to fire the injector. If the problem remains, this sequence of events will be repeated until the problem is corrected.
2-5 Cylinder #2 Injector : Current Below Normal The ECM detects an open circuit. The code is logged.
The ECM continues to fire the injector solenoid.
2-6 Cylinder #2 Injector : Current Above Normal The ECM detects a short circuit. The code is logged.
The ECM will disable the solenoid circuit. The ECM will periodically try to fire the injector. If the short circuit remains, this sequence of events will be repeated until the problem is corrected.
2-11 Cylinder #2 Injector : Other Failure Mode The ECM detects a problem in the circuit for the injector. The code is logged.
The ECM will periodically try to fire the injector. If the problem remains, this sequence of events will be repeated until the problem is corrected.
3-5 Cylinder #3 Injector : Current Below Normal The ECM detects an open circuit. The code is logged.
The ECM continues to fire the injector solenoid.
3-6 Cylinder #3 Injector : Current Above Normal The ECM detects a short circuit. The code is logged.
The ECM will disable the solenoid circuit. The ECM will periodically try to fire the injector. If the short circuit remains, this sequence of events will be repeated until the problem is corrected.
3-11 Cylinder #3 Injector : Other Failure Mode The ECM detects a problem in the circuit for the injector. The code is logged.
The ECM will periodically try to fire the injector. If the problem remains, this sequence of events will be repeated until the problem is corrected.
4-5 Cylinder #4 Injector : Current Below Normal The ECM detects an open circuit. The code is logged.
The ECM continues to fire the injector solenoid.
4-6 Cylinder #4 Injector : Current Above Normal The ECM detects a short circuit. The code is logged.
The ECM will disable the solenoid circuit. The ECM will periodically try to fire the injector. If the short circuit remains, this sequence of events will be repeated until the problem is corrected.
4-11 Cylinder #4 Injector : Other Failure Mode The ECM detects a problem in the circuit for the injector. The code is logged.
The ECM will periodically try to fire the injector. If the problem remains, this sequence of events will be repeated until the problem is corrected.
5-5 Cylinder #5 Injector : Current Below Normal The ECM detects an open circuit. The code is logged.
The ECM continues to fire the injector solenoid.
5-6 Cylinder #5 Injector : Current Above Normal The ECM detects a short circuit. The code is logged.
The ECM will disable the solenoid circuit. The ECM will periodically try to fire the injector. If the short circuit remains, this sequence of events will be repeated until the problem is corrected.
5-11 Cylinder #5 Injector : Other Failure Mode The ECM detects a problem in the circuit for the injector. The code is logged.
The ECM will periodically try to fire the injector. If the problem remains, this sequence of events will be repeated until the problem is corrected.
6-5 Cylinder #6 Injector : Current Below Normal The ECM detects an open circuit. The code is logged.
The ECM continues to fire the injector solenoid.
6-6 Cylinder #6 Injector : Current Above Normal The ECM detects a short circuit. The code is logged.
The ECM will disable the solenoid circuit. The ECM will periodically try to fire the injector. If the short circuit remains, this sequence of events will be repeated until the problem is corrected.
6-11 Cylinder #6 Injector : Other Failure Mode The ECM detects a problem in the circuit for the injector. The code is logged.
The ECM will periodically try to fire the injector. If the problem remains, this sequence of events will be repeated until the problem is corrected.

Perform this procedure under conditions that are identical to the conditions that exist when the problem occurs. Typically, problems with the injector solenoid occur when the engine is warmed up and/or when the engine is under vibration (heavy loads).

These engines have Electronic Unit Injectors (EUI) that are mechanically actuated and electronically controlled. The ECM sends a 105 volt pulse to each injector solenoid. The pulse is sent at the proper time and at the correct duration for a given engine load and speed. The solenoid is mounted on top of the fuel injector body.

If an open is detected in the solenoid circuit, a diagnostic code is generated. The ECM continues to try to fire the injector. If a short is detected, a diagnostic code is generated. The ECM will disable the solenoid circuit. The ECM will periodically try to fire the injector. If the short circuit remains, this sequence of events will be repeated until the problem is corrected.

Note: Refer to Illustration 2. Two injector solenoids share a supply wire. For this reason, an open circuit or a short circuit in a supply wire or a connector could cause diagnostic codes for two injector solenoids. Note that a diagnostic code for a single injector indicates that the problem is most likely in the return wire or a connector in the return circuit.

Caterpillar Electronic Technician (ET) includes the following tests that aid in troubleshooting the injector solenoids:

“Cylinder Cutout Test”

The “Cylinder Cutout Test” is used on an engine in order to determine the individual cylinder performance while the engine is running. As one or more cylinders are cut out during the test, the “Cylinder Cutout Test” uses the “Fuel Position” of each injector in order to evaluate the performance of the remaining cylinders that are firing. As the different cylinders are cut out, a comparison of the change in “Fuel Position” is used to identify cylinders that are weak or misfiring. One reason for a cylinder that is weak or misfiring is an injector that is malfunctioning mechanically.

During the test, when a good injector is cut out, the “Fuel Position” of the remaining injectors will show a consistent change. This consistent change in the “Fuel Position” is caused by the remaining injectors that are compensating for the cut out injector. If a malfunctioning injector is cut out, the “Fuel Position” will not show a proportional change. This unbalanced change is the result of the smaller quantity of fuel that is needed to compensate for the power loss from the malfunctioning injector. The “Cylinder Cutout Test” is used to isolate a malfunctioning injector in order to avoid replacement of injectors that are in good repair.

Note: Prior to running the “Cylinder Cutout Test”, all active diagnostic codes must be repaired.

“Injector Solenoid Test”

Use the “Injector Solenoid Test” to diagnose an open circuit or a short circuit in the wiring for the injector solenoids. While the engine is off, the “Injector Solenoid Test” briefly activates each injector solenoid. A good solenoid will create an audible click when the solenoid is activated. After performing the test, Cat ET will indicate the status of the solenoid as “OK”, “Open”, or “Short”.


Illustration 1 g01147070
Electronic unit injector


Typical schematic for the injector solenoids

Test Step 1. Inspect the Electrical Connectors and the Wiring

  1. Remove electrical power from the ECM.


Illustration 3 g01139425
ECM
(1) J1/P1 connectors
(2) J2/P2 connectors

  1. Thoroughly inspect the wire connections at the ECM connector J2/P2 and at the valve cover connector. Refer to Troubleshooting, “Electrical Connectors – Inspect” for details.

    Illustration 4 g01430793
Terminal locations at the P2 ECM connector

(P2-5) Injector 1 & 2 return

(P2-6) Injector 1 supply

(P2-12) Injector 2 supply

(P2-17) Injector 3 & 4 return

(P2-18) Injector 3 supply

(P2-22) Injector 4 supply

(P2-27) Injector 5 & 6 return

(P2-28) Injector 5 supply

(P2-34) Injector 6 supply


Illustration 5 g01409176
Terminal locations at the valve cover connector

(Terminal 1) Injector 1 supply

(Terminal 2) Injector 2 supply

(Terminal 3) Injector 3 supply

(Terminal 4) Injector 4 supply

(Terminal 5) Injector 5 supply

(Terminal 6) Injector 6 supply

(Terminal 8) Injector 5 & 6 return

(Terminal 10) Injector 3 & 4 return

(Terminal 12) Injector 1 & 2 return

  1. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and each of the wires that are associated with injector solenoids.

 

  1. Check the allen head screw on each ECM connector for the proper torque. Refer to Troubleshooting, “Electrical Connectors – Inspect” for the correct torque values.

 

  1. Check the harness and wiring for abrasions and for pinch points from the injectors to the ECM.

Expected Result:

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

Results:

 

  • OK – The connectors and the wiring 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 Logged Diagnostic Codes for the Injector Solenoids

 

  1. Connect Cat ET to the data link connector. Refer to Troubleshooting, “Electronic Service Tools”.

 

  1. Restore electrical power to the ECM.

 

  1. Check for logged diagnostic codes for the injector solenoids on Cat ET.

Expected Result:

There are no logged diagnostic codes for the injector solenoids.

Results:

 

  • OK – No diagnostic codes have been logged. The injector solenoids are operating correctly. There may be a mechanical problem with the injector’s fuel delivery. Proceed to Test Step 3.
  • Not OK – One or more diagnostic codes have been logged. There may be an electrical problem in the circuit for the injector. Proceed to Test Step 4.

Test Step 3. Perform the “Cylinder Cutout Test”

 

  1. Start the engine.

 

  1. Allow the engine to warm up to normal operating temperature (approximately 77 °C (171 °F)).

 

  1. After the engine is warmed to operating temperature, access the “Cylinder Cutout Test” by accessing the following display screens in order:
    • “Diagnostics”
    • “Diagnostic Tests”
    • “Cylinder Cutout Test”

 

  1. Shut off all parasitic loads which could affect the results of the test.

 

  1. Select the start button at the bottom of the screen for the cylinder cutout test on Cat ET.

 

  1. Follow the instructions that are provided in the cylinder cutout test. The cylinder cutout tests are interactive so the procedure is guided to the finish. The cylinder cutout test will set the correct engine speed for the application.

Expected Result:

The variation of the fuel rate for all cylinders is within specifications.

Results:

 

  • OK – The cylinder cutout test indicates that all of the injectors are operating correctly.Repair: If a problem with the fuel system is suspected and diagnostic codes are not active or logged, refer to Systems Operation/Testing and Adjusting for information that is related to the low pressure fuel system.If a diagnostic code results from running the “Cylinder Cutout Test”, proceed to Test Step 4.
  • Not OK – The cylinder cutout test indicates that at least one of the injectors is not operating correctly.Repair: Verify that the engine valve lash for that injector is set correctly. Rerun the “Cylinder Cutout Test”. If the problem is still present, replace the injector.STOP

Test Step 4. Perform the “Injector Solenoid Test”

 

  1. Start the engine.

 

  1. Allow the engine to warm up to normal operating temperature (approximately 77 °C (171 °F)).

 

  1. Stop the engine.

 

  1. Restore electrical power to the ECM.

 

  1. Access the “Injector Solenoid Test” by accessing the following display screens in order:
    • “Diagnostics”
    • “Diagnostic Tests”
    • “Injector Solenoid Test”

 

  1. Activate the “Injector Solenoid Test”.

 

  1. As each solenoid is energized by the ECM an audible click can be heard at the valve cover. Ensure the activation of each solenoid by comparing the location of the click with the progress that is displayed on Cat ET.

 

  1. Perform the injector solenoid test at least two times.

Expected Result:

All cylinders indicate “OK” on Cat ET.

Results:

 

  • OK – There is not an electronic problem with the injectors at this time.Repair: The problem appears to be resolved. The problem was probably caused by a poor electrical connection in a connector.If the codes continue to be logged, refer to Troubleshooting, “Electrical Connectors – Inspect”.If the engine is misfiring or if the engine has low power, refer to Troubleshooting, “Engine Misfires, Runs Rough or Is Unstable” or Troubleshooting, “Power Is Intermittently Low or Power Cutout Is Intermittent”.STOP
  • Not OK – “Open” – Note the cylinder that indicates “Open”. Proceed to Test Step 5.
  • Not OK – “Short” – Note the cylinder that indicates “Short”. Proceed to Test Step 6.

Test Step 5. Check the Harness between the ECM and the Valve Cover Base for an Open Circuit

  1. Remove electrical power from the ECM.

 

  1. Disconnect the valve cover connector for the injector harness at the valve cover base.

 

  1. Fabricate a jumper wire that will be long enough to short circuit the different terminals on the valve cover connector. Crimp connector pins on both ends of the jumper wire.


Illustration 6 g01409177
Terminal locations at the valve cover connector

(Terminal 1) Injector 1 supply

(Terminal 2) Injector 2 supply

(Terminal 3) Injector 3 supply

(Terminal 4) Injector 4 supply

(Terminal 5) Injector 5 supply

(Terminal 6) Injector 6 supply

(Terminal 8) Injector 5 & 6 return

(Terminal 10) Injector 3 & 4 return

(Terminal 12) Injector 1 & 2 return

  1. Insert one end of the jumper wire into the connector socket for the suspect injector’s supply wire. Insert the other end of the jumper wire into the connector socket for the suspect injector’s return wire. This will replace the injector solenoid with a short circuit.

 

  1. Restore electrical power to the ECM.

 

  1. Perform the “Injector Solenoid Test” at least two times.

 

  1. Repeat this test for each suspect circuit. Stop the “Injector Solenoid Test” before handling the jumper wire. Restore the wiring to the original configuration.

Expected Result:

Cat ET displays “Short” for each of the circuits that were jumpered.

Results:

 

  • OK – Cat ET displays “Short” for each circuit that was jumpered. The harness between the ECM and the valve cover connector does not have an open circuit. Proceed to Test Step 7.
  • Not OK – Cat ET displays “Open” for the cylinder with the jumper wire. There is a problem in the wiring between the ECM and the valve cover connector. Proceed to Test Step 8.

Test Step 6. Check the Harness between the ECM and the Valve Cover Base for a Short Circuit

  1. Remove electrical power from the ECM.

 

  1. Disconnect the valve cover connector for the injector harness.

 

  1. Restore electrical power to the ECM.

 

  1. Perform the “Injector Solenoid Test” at least two times.

Expected Result:

All of the cylinders indicate “Open” on Cat ET.

Results:

 

  • OK – All cylinders indicate “Open” on Cat ET. The harness between the ECM and the valve cover connector does not have a short circuit. Proceed to Test Step 7.
  • Not OK – One or more cylinders indicate “Short” on Cat ET. Note the cylinders that indicate “Short”. Proceed to Test Step 8.

Test Step 7. Check the Injector Harness Under the Valve Cover for an Open Circuit or for a Short Circuit

  1. Remove electrical power from the ECM.

 

  1. Remove the valve cover in order to gain access to the suspect injector.

 

  1. Disconnect the harness connector from the suspect injector.


Illustration 7 g01147088
Connector terminals for the injector solenoid

  1. Thoroughly clean the terminals on the injector solenoid and on the harness connector.

 

  1. Use a jumper wire to short circuit the connector terminals for the suspect injector. This will effectively replace the injector solenoid with a short circuit.

 

  1. Restore electrical power to the ECM.

 

  1. Perform the “Injector Solenoid Test” at least two times.Note: The injector solenoid that shares the supply wire of the injector that is short circuited may indicate a false test result. Disregard this test result.

 

  1. Remove electrical power from the ECM.

 

  1. Remove the jumper wire from the injector connector. This will effectively replace the injector solenoid with an open circuit.

 

  1. Restore electrical power to the ECM.

 

  1. Perform the “Injector Solenoid Test” at least two times.

 

  1. Remove electrical power from the ECM.

Expected Result:

Cat ET displays “Short” for the cylinder with the jumper wire and “Open” when the jumper wire is removed.

Results:

 

  • OK – Cat ET displays the correct status during the test. The harness wiring is OK.Repair: Use a multimeter to check the resistance of the suspect injector solenoid.The correct resistance of each injector solenoid is 1.06 ± 0.05 Ohms.If the resistance of the solenoid is not within specifications replace the faulty injector. Verify that the problem is resolved.If the resistance of the solenoid is within specifications the problem may be intermittent. If the problem is intermittent, refer to Troubleshooting, “Electrical Connectors – Inspect”. Verify that the repair eliminates the problem.

    STOP

     

  • Not OK – Cat ET did not display the correct status during the test. There is a problem with the injector harness under the valve cover. There may be a problem with a connector.Repair: Repair the wiring and/or the connector, when possible. Replace parts, if necessary. Verify that the problem is resolved.

    STOP

Test Step 8. Check the ECM for Proper Operation

  1. Remove electrical power from the ECM.

 

  1. Fabricate a jumper that is long enough to reach from the P2 ECM connector to the engine ground stud. Crimp a socket terminal to one end of the jumper wire.

 

  1. Disconnect the P2 connector.

 

  1. Remove the supply wire for the suspect injector from the ECM connector. Install the jumper wire into the socket.

 

  1. Connect the J2/P2 ECM connector.

 

  1. Verify that the ECM will detect an open circuit for the suspect injector: 
    1. Ensure that the jumper wire is not in contact with a ground source or another circuit. Do not touch the jumper wire during the test. A strong electrical shock hazard is present at the jumper wire while the test is running.

     

    1. Restore electrical power to the ECM.

     

    1. Perform the “Injector Solenoid Test” at least two times.Cat ET displays “Open” for the two injectors that share the supply wire.

     

    1. Remove electrical power from the ECM.

 

  1. Verify that the ECM detects a short circuit for the suspect injector: 
    1. Connect the jumper wire to the engine ground stud. Do not touch the jumper wire during the test. A strong electrical shock hazard is present at the jumper wire while the test is running.

     

    1. Restore electrical power to the ECM.

     

    1. Perform the “Injector Solenoid Test” at least two times.Cat ET displays “Short” for the two injectors that share the supply wire.

     

    1. Remove electrical power from the ECM.

Expected Result:

Cat ET displays the correct status for each test circuit.

Results:

 

  • OK – The ECM detects the correct status of the circuit. There is an open circuit or a short circuit in the engine harness. There may be a problem with a connector.Repair: Inspect the connectors for moisture and for corrosion. Repair the wiring and/or the connector, when possible. Replace parts, if necessary. Clear all diagnostic codes after you complete this test step.Verify that the problem is resolved.

    STOP

     

  • Not OK – The ECM does not detect the correct status of the circuit.Repair: There is a problem with the ECM. Replace the ECM. Refer to Troubleshooting, “ECM – Replace”. Verify that the problem is resolved.

    STOP

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