3126E On-highway Engine Caterpillar

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).

The engines use Hydraulic Electronic Unit Injectors that are hydraulically actuated and electronically energized. The solenoid is mounted on top of the fuel injector body.

"Cylinder Cutout Test"

The "Cylinder Cutout Test" on the Caterpillar Electronic Technician (Cat ET) should be used to diagnose a bad injector while the engine is running. All active diagnostic codes must be repaired before running the "Cylinder Cutout Test". When a good injector is cut out, the "Fuel Position" should change. The change in the fuel position is caused by the other cylinders that are compensating for the cut out cylinder. If a bad cylinder is cut out, the "Fuel Position" will not change. The "Cylinder Cutout Test" should be used to isolate the bad cylinder in order to avoid replacement of good injectors.

"Injector Solenoid Test"

The "Injector Solenoid Test" on Cat ET should be used to aid in diagnosing an open circuit or a short circuit diagnostic code while the engine is not running. The "Injector Solenoid Test" will send a signal to each solenoid. The electronic service tool will indicate the status of the solenoid as "OK", "Open", or "Short". An open circuit or a short circuit in the common wire will cause two cylinders to have diagnostic codes.

Note: The "Injector Solenoid Test" will not help find leaks in the high pressure oil system.

Illustration 1	g00864955
Left side view and top view of engine

Illustration 2	g00782844
Circuit schematic for the injectors

Illustration 3	g00864998
P2 ECM connector

Illustration 4	g00723455
P300 Injector harness connector

Test Step 1. Inspect Electrical Connectors and Wiring

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Electrical shock hazard. The electronic unit injector system uses 90-120 volts.

1. Turn the key switch to the OFF position. A strong electrical shock hazard is present if the key switch is not turned off.

2. Thoroughly inspect the J2/P2 ECM connector and the J300/P300 injector harness connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector and the J300/P300 injector harness connector that are associated with injector solenoids.

4. Check the ECM connector (allen head screw) for the proper torque of 6.0 N·m (55 lb in).

5. Check the J300/P300 injector harness connector in order to ensure the proper mating of the connector.

6. Check the harness and wiring for abrasion and pinch points from the injectors to the ECM.

Expected Result:

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

Results:

• OK - Proceed to Test Step 2.

• Not OK -

  Repair: Perform the following 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 Regarding Injector Solenoids

1. Connect Cat ET to the data link connector.

2. Turn the key switch to the ON position.

3. Check for logged diagnostic codes that are related to the injector solenoids on Cat ET.

Expected Result:

One or more diagnostic codes that are related to the injector solenoids have been logged:

Results:

• OK - One or more diagnostic codes have been logged. Proceed to Test Step 4.

• Not OK - No diagnostic codes have been logged. Proceed to Test Step 3.

Test Step 3. Check the Variation of the Injectors between Cylinders

1. When possible, put the truck on a dynamometer.

2. Start the engine.

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

4. 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"

5. Enable the cooling fan, if the fan is not controlled by the ECM. If the ECM controls the cooling fan, the cooling fan will start automatically when the test begins.

6. Shut off all parasitic loads such as the air conditioning and the air compressors which could affect the results of the test.

7. Set the engine speed to 1000 ± 20 rpm.

8. Select the start button at the bottom of the screen for the Cylinder Cutout test on Cat ET.

9. Select the "4 Cylinder Cutout Test" which is the default test.

10. 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.

    Note: The "Manual Cylinder Cutout Test" is also available. Access the manual test by selecting the "Change" button on the screen for the Cylinder Cutout test. The "4 Cylinder Cutout Test" is the recommended starting procedure. The automated tests run twice collecting data. The two sets of data are analyzed and an "OK" or "Not OK" result is displayed.

11. Check for active diagnostic codes and logged diagnostic codes that are related to the injector solenoids.

Expected Result:

All cylinders indicate "OK" on Cat ET.

Results:

• OK - All cylinders indicate "OK".

  Repair: If the engine is misfiring or if the engine has low power, refer to Troubleshooting, "Engine Misfires, Runs Rough or Is Unstable" and Troubleshooting, "Low Power/Poor or No Response to Throttle".

  If a diagnostic code results from running the Cylinder Cutout test, proceed to Test Step 4.

• Not OK - One or more cylinders displayed "Not OK" during the test. Proceed to Test Step 4.

Test Step 4. Test the Injector Solenoids

1. Start the engine.

2. Allow the engine to warm up to 77 °C (171 °F) which is the normal operating temperature.

3. Stop the engine.

4. Turn the key switch to the ON position.

5. After the engine is warmed to operating temperature, access the "Injector Solenoid Test" by accessing the following display screens in order:
   • "Diagnostics"

   • "Diagnostic Tests"

   • "Injector Solenoid Test"

6. Activate the test.

   Note: Do not confuse the "Injector Solenoid Test" with the "Cylinder Cutout Test". The "Cylinder Cutout Test" is used to shut off fuel to a specific cylinder while the engine is running. The "Injector Solenoid Test" is used to actuate the injector solenoids. This allows the click of the injector solenoids to be heard when the engine is not running in order to determine that the circuit is functioning properly.

7. As each solenoid is energized by the ECM, an audible click can be heard at the valve cover.

8. Perform the "Injector Solenoid Test" at least two times.

Expected Result:

All cylinders indicate "OK".

Results:

• OK - There is not an electronic problem with the injectors at this time.

  Repair: If the "Cylinder Cutout Test" returned a "Not OK" for any injector, refer to Troubleshooting, "Engine Misfires, Runs Rough or Is Unstable".

  STOP

• Open - Note the cylinders that indicate "Open". Proceed to Test Step 5.

• Short - Note the cylinders that indicate "Short". Proceed to Test Step 8.

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

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Electrical shock hazard. The electronic unit injector system uses 90-120 volts.

1. Turn the key switch to the OFF position. A strong electrical shock hazard is present if the key switch is not turned off.

2. Disconnect the P300 injector harness connector from the valve cover base.

3. Turn the key switch to the ON position.

4. Fabricate a jumper wire 100 mm (4 inch) long with Deutsch pins on both ends of the wire.

5. Insert one end of the jumper wire into the common socket for the suspect injector. Insert the other end of the jumper wire into the socket for the suspect injector. For example, if injector 5 is the problem injector, insert the jumper wire between P300:5 (Injector Cylinder 5) and P300:8 (Injector Common Cylinders 5 & 6) of the P300 injector harness connector.

6. Perform the "Injector Solenoid Test" at least two times.

7. Repeat this test for each suspect injector. Stop the "Injector Solenoid Test" before handling the jumper wires.

Expected Result:

Cat ET displays "Short" for the cylinder with the jumper wire.

Results:

• OK - The harness between the ECM and the valve cover base is OK. Proceed to Test Step 6.

• Not OK - There is a problem between the ECM and the valve cover base. Proceed to Test Step 7.

Test Step 6. Check the Injector Harness Under the Valve Cover

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Electrical shock hazard. The electronic unit injector system uses 90-120 volts.

1. Turn the key switch to the OFF position. A strong electrical shock hazard is present if the key switch is not turned off.

2. Remove the valve cover.

3. Disconnect the harness from the suspect injector. Disconnect the harness from the injector that shares the same injector common line.

   Note: If both injectors that share a common wire indicate "Open", inspect the common wire under the valve cover for problems. The open circuit is probably caused by an open in the common wire.

4. Thoroughly clean the terminals on both injectors and the harness connectors.

5. Exchange the harness between the two injectors that share the common line.

6. Turn the key switch to the ON position.

7. Perform the "Injector Solenoid Test" at least two times.

Expected Result:

Exchanging the harness between the two injectors caused the problem to move to the other injector on Cat ET.

Results:

• OK - The injector may be faulty.

  Repair: Replace the faulty injector.Restore the wiring to the proper injectors.Perform the "Injector Solenoid Test".Verify that the repair eliminates the problem.

  STOP

• Not OK - There is a problem with the injector harness under the valve cover.

  Repair: Repair the injector harness or replace the injector harness under the valve cover.Verify that the repair eliminates the problem.

  STOP

Test Step 7. Check the ECM for an Open Circuit

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Electrical shock hazard. The electronic unit injector system uses 90-120 volts.

1. Turn the key switch to the OFF position. A strong electrical shock hazard is present if the key switch is not turned off.

2. Disconnect the P2 ECM connector from the ECM. Connect a 140-2266 Cable (Seventy-Pin Breakout) to the ECM. Do not connect the engine harness to the breakout T.

3. Use a jumper wire to short between the socket of the suspect injector and the common socket of the suspect injector.

4. Turn the key switch to the ON position.

5. Perform the "Injector Solenoid Test" at least two times.

Expected Result:

Cat ET displays "Short" for the cylinder with the jumper wire.

Note: When the engine harness is disconnected, all of the diagnostic codes for supply voltage to the sensors will be active. This is normal. Clear all of these diagnostic codes after completing this test step.

Results:

• OK - The ECM is OK.

  Repair: If two injectors that share a common wire indicate "Open", inspect the common wire for problems. The open circuit is probably caused by an open in the common wire.Repair the engine harness or replace the engine harness, as required.Verify that the repair eliminates the problem.

  STOP

• Not OK - There may be a problem with the ECM.

  Repair: Temporarily connect a test ECM.Remove the breakout T and reconnect the P2 ECM connector.Perform the "Injector Solenoid Test".If the test ECM fixes the problem, reconnect the suspect ECM.If the problem returns with the suspect ECM, replace the ECM.Verify that the repair eliminates the problem.

  STOP

Test Step 8. Check the Harness between the ECM and the Valve Cover Base for a Short Circuit

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Electrical shock hazard. The electronic unit injector system uses 90-120 volts.

1. Turn the key switch to the OFF position. A strong electrical shock hazard is present if the key switch is not turned off.

2. Disconnect the P300 injector harness connector from the valve cover base.

3. Turn the key switch to the ON position.

4. Perform the "Injector Solenoid Test" at least two times.

Expected Result:

All cylinders indicate "Open".

Results:

• OK - All cylinders indicate "Open".

  Repair: Reconnect the P300 injector harness connector.

  Proceed to Test Step 10.

• Not OK - One or more cylinders indicate "Short". Note the cylinders that indicate "Short". Proceed to Test Step 9.

Test Step 9. Check the ECM for a Short Circuit

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Electrical shock hazard. The electronic unit injector system uses 90-120 volts.

1. Turn the key switch to the OFF position. A strong electrical shock hazard is present if the key switch is not turned off.

2. Disconnect the P2 ECM connector from the ECM and check for evidence of moisture entry.

3. Turn the key switch to the ON position.

4. Perform the "Injector Solenoid Test" at least two times.

Expected Result:

All cylinders indicate "Open" when the P2 ECM connector is disconnected from the ECM.

Note: When the engine harness is disconnected, all of the diagnostic codes for supply voltage to the sensors will be active. This is normal. Clear all of these diagnostic codes after completing this test step.

Results:

• OK - The short circuit is in the engine harness.

  Repair: The problem is most likely in the supply wire to the injector. Inspect the connectors for moisture and corrosion. Also, check the supply wire for exposed wires.Repair the engine harness or replace the engine harness, as required. Clear all diagnostic codes after completing this test step.Verify that the repair eliminates the problem.

  STOP

• Not OK - There may be a problem with the ECM.

  Repair: Temporarily connect a test ECM.Reconnect the P2 ECM connector.Perform the "Injector Solenoid Test".If the test ECM fixes the problem, reconnect the suspect ECM.If the problem returns with the suspect ECM, replace the ECM.Verify that the repair eliminates the problem.

  STOP

Test Step 10. Check the Engine Harness Under the Valve Cover for a Short Circuit

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Electrical shock hazard. The electronic unit injector system uses 90-120 volts.

1. Turn the key switch to the OFF position. A strong electrical shock hazard is present if the key switch is not turned off.

2. Remove the valve cover.

3. Disconnect each of the injectors that indicate a "Short" from the wiring harness. Ensure that each of the connectors from the disconnected injector harness does not touch other components and short to ground.

4. Turn the key switch to the ON position.

5. Perform the "Injector Solenoid Test" at least two times.

Expected Result:

All of the injectors that were disconnected indicate "Open".

Results:

• OK - All of the injectors that were disconnected indicate "Open".

  Repair: Leave the injector wires disconnected. Neither of the injector wires are shorted to the engine.

  Proceed to Test Step 11.

• Not OK - One or more of the injectors that were disconnected indicate "Short".

  Repair: The problem is most likely in the supply wire to the injector. Inspect the connectors for moisture and corrosion. Also, check the supply wire for exposed wires.Repair the injector harness or replace the injector harness under the valve cover.Verify that the repair eliminates the problem.

  STOP

Test Step 11. Check for a Short Circuit in the Injector Common Line

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Electrical shock hazard. The electronic unit injector system uses 90-120 volts.

1. Turn the key switch to the OFF position. A strong electrical shock hazard is present if the key switch is not turned off.

2. Disconnect the P2 ECM connector from the ECM.

3. Locate the common line for the problem injector in the P2 connector. Measure the resistance from the terminal to the engine ground stud connection.

Expected Result:

The resistance is greater than 10 Ohms.

Results:

• OK - The resistance is greater than 10 Ohms.

  Repair: Reconnect the J2/P2 ECM connector.Replace the faulty injector.Perform the "Injector Solenoid Test".Verify that the repair eliminates the problem.

  STOP

• Not OK - There is a short in the injector harness.

  Repair: Disconnect the J300/P300 injector harness connector.Measure the resistance of the common wire between the P2 ECM connector and the engine ground stud.If the resistance is less than 10 Ohms, the problem is in the common wire between the ECM and the valve cover base.If the resistance is greater than 10 Ohms, the problem is in the common wire under the valve cover.Repair the injector harness or replace the injector harness.Perform the "Injector Solenoid Test".Verify that the repair eliminates the problem.

  STOP