C7.1 Engines For Caterpillar Built Machines Caterpillar

This procedure covers the following diagnostic code:

Use this procedure if there is a suspected fault in the glow plug start aid circuit or the glow plugs.

The following background information is related to this procedure:

The starting aid is used to improve the engine starting when the engine is cold. With the keyswitch in the ON position, the Electronic Control Module (ECM) monitors the coolant temperature and the intake manifold air temperature. These temperatures determine if the glow plugs need to be switched ON. If the glow plugs are required, then the ECM will activate the starting aid relay for a controlled period. While the glow plug start aid relay is activated, the glow plug start aid relay will supply power to the glow plugs.

The engine is equipped with ether injection. Glow plugs are used for temperatures that are between 5° C (41° F) and −25 °C (−13 °F). If the ambient temperature is below −25 °C (−13 °F), the glow plugs are disabled and ether injection is used.

Electronic Service Tool Test Aid

The electronic service tool includes the test "Glow Plug Start Aid Override Test". This test will assist the analysis of the cold starting aid.

Overview of the Glow Plug Start Aid Override Test

This glow plug start aid override test switches on the cold starting aid when the engine is not running. The glow plug start aid override test aids the analysis of the circuit for the glow plug start aid relay.

Illustration 1	g02456097
Schematic for the glow plug starting aid circuit

Illustration 2	g02456117
View of the pin locations on the P1 connector for the glow plug starting aid circuit (10) Glow plug start aid control (59) Return

Test Step 1. Inspect Electrical Connectors and Wiring

1. Check that the fuses are not blown.

2. Inspect the terminals on the glow plug start aid relay and then inspect the connector on the flying lead from the relay. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Inspect the bus bar for the glow plugs. Ensure that the nuts that secure the bus bar to each glow plug are tightened to a torque of 2 N·m (17 lb in). Ensure that the bus bar is not shorted to the engine.

4. Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the glow plug starting aid.

5. Check the screw for the ECM connector for the correct torque of 6 N·m (53 lb in).

6. Check the harness for abrasion and pinch points from the glow plugs back to the ECM.

Results:

• All connectors, pins, and sockets are correctly coupled and/or inserted. The harness is free of corrosion, abrasion, and pinch points. The fuses are not blown. The bus bar is secured to the glow plugs and not shorted to ground. - Proceed to Test Step 2.

• There is a fault with the harness and connectors -

  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 correctly connected. Replace blown fuses.Use the electronic service tool in order to clear all logged diagnostic codes and then verify that the repair has eliminated 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.

   Note: Do not start the engine.

3. Use the electronic service tool to select the "Glow Plug Start Aid Override Test" in order to turn on the power for the glow plugs.

4. Check for active diagnostic codes or recently logged diagnostic codes.

Results:

• Diagnostic code 2246-6 is active or recently logged - Proceed to Test step 3.

• An active diagnostic code or a recently logged diagnostic code was not displayed. - There may be a fault with the glow plug switched power circuit or there may be an open circuit in the relay coil circuit. The ECM does not monitor the status of these conditions. Proceed to Test Step 5.

Test Step 3. Disconnect the Relay

1. Turn the keyswitch to the OFF position.

2. Disconnect the glow plug start aid relay.

3. Use the electronic service tool to select the "Glow Plug Start Aid Override Test" in order to turn on the power for the glow plugs.

4. Use the electronic service tool to check for an active 2246-6 diagnostic code.

Results:

• A 2246-6 diagnostic code is active at this time. - There is a short in the circuit for the relay coil. Reconnect the relay. Proceed to Test Step 4.

• The 2246-6 diagnostic code is not active with the relay disconnected. - There is a fault in the relay.

  Repair: Perform the following repair:

  1. Install a replacement relay.

  2. Use the electronic service tool to perform the "Glow Plug Start Aid Override Test".

  3. Confirm that the fault has been eliminated.

  STOP

Test Step 4. Disconnect the Relay at the ECM

1. Disconnect the P1 connector.

2. Inspect the P1 connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

3. Remove the wire from P1:10.

4. Reconnect the P1 connector.

5. Use the electronic service tool to select the "Glow Plug Start Aid Override Test" in order to turn on the power for the glow plugs.

6. Use the electronic service tool to check for an active 2246-6 diagnostic code.

7. Disconnect the P1 connector.

8. Reconnect the wire to P1:10.

9. Reconnect the P1 connector.

Results:

• A 2246-6 diagnostic code is active at this time. - The wiring for the glow plug start aid relay is not shorted. Proceed to Test Step 8.

• The 2246-6 diagnostic code is no longer active. - The wiring between P1:10 and the ECM is shorted.

  Repair: Perform the following repair:

  1. Repair the faulty wiring or replace the faulty wiring.

  2. Use the electronic service tool to perform the "Glow Plug Start Aid Override Test".

  3. Confirm that the fault has been eliminated.

  STOP

Test Step 5. Check the Operation of the Glow Plugs

1. Place a suitable clamp-on ammeter on the power supply wire.

2. Use the electronic service tool to select the "Glow Plug Start Aid Override Test" in order to turn on the power for the glow plugs.

3. Wait for 20 seconds and then note the reading on the Clamp-on ammeter.

Expected Result:

The ammeter reading is approximately 4.5 Amps.

Results:

• The reading on the clamp-on ammeter is zero. - There is a fault in the circuit for the glow plugs. Proceed to Test Step 6.

• The reading on the clamp-on ammeter is between zero and the expected reading for the system. - Proceed to Test Step 9.

• The reading on the clamp-on ammeter is correct. - The glow plugs are operating correctly.STOP

Test Step 6. Create a Short Circuit at the Relay Connector

1. Turn the keyswitch to the OFF position.

2. Disconnect the connector for the glow plug start aid relay.

3. Fabricate a jumper wire that is 150 mm (6 inch) long.

4. Install the jumper between Test Point 1 and test Point 2 on the harness connector for the relay.

5. Turn the keyswitch to the ON position.

6. Use the electronic service tool to select the "Glow Plug Start Aid Override Test" in order to turn on the power for the glow plugs.

7. Use the electronic service tool to check for an active 2246-6 diagnostic code.

8. Remove the jumper. Leave the relay disconnected.

Results:

• A 2246-6 diagnostic code is not active with the jumper installed. - Proceed to Test Step 7.

• A 2246-6 diagnostic code is active with the jumper installed. - The wiring for the relay coil is OK. Proceed to Test Step 10.

Test Step 7. Check the Wiring Between the ECM and the Relay

1. Turn the keyswitch to the OFF position.

2. Disconnect the P1 connector.

3. Inspect the P1 connector. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.

4. Measure the resistance between Test Point 2 on the harness connector for the relay and P1:10.

5. Measure the resistance between Test Point 1 on the harness connector for the relay and P1:59.

Expected Result:

Each resistance measurement should be less than 10,000 Ohms.

Results:

• OK - Each resistance measurement was less than 10,000 Ohms. Proceed to Test Step 8

• Not OK - One or both of the resistance measurements was more than 10,000 Ohms. The fault is in the wiring between the relay and the ECM.

  Repair: Perform the following repair:

  1. Repair or replace any wiring that failed the resistance check.

  2. Use the electronic service tool to perform the "Glow Plug Start Aid Override Test".

  3. Confirm that the fault has been eliminated.

  STOP

Test Step 8. Check the ECM

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 a Cat 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. Use the electronic service tool in order to clear all logged diagnostic codes.

5. Use the electronic service tool in order to perform a "Glow Plug Start Aid Override Test".

Results:

• OK - The replacement ECM functions correctly. Performing the "Glow Plug Start Aid Override Test" energizes the glow plugs.

  Repair: Perform the following procedure:

  1. Reconnect the suspect ECM.

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

  3. 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 fault is still present with the replacement ECM. Do not use the replacement ECM.

  Repair: Contact the Technical Communicator at a Cat dealer

  STOP

Test Step 9. Test the Continuity of the Glow Plugs

1. Disconnect the power supply and remove the bus bar from the glow plugs.

2. Use a suitable digital multimeter to check continuity (resistance). Turn the audible signal on the digital multimeter ON.

3. Place one probe on the connection for one of the glow plugs and the other probe to a suitable ground. The digital multimeter should make an audible sound.

4. Repeat the continuity check on the remaining glow plugs.

Expected Result:

One or more glow plugs do not have continuity.

Results:

• OK - All glow plugs display continuity. Repeat this procedure from Test Step 1.

• Not OK - One or more of the glow plugs do not display continuity.

  Repair: Perform the following procedure:

  1. Replace any glow plugs that do not display continuity.

  2. Confirm that the fault has been eliminated.

  STOP

Test Step 10. Check the Relay Coil for an Open Circuit

1. Turn the keyswitch to the OFF position.

2. Measure the resistance from Test Point 1 to Test Point 2 on the harness connector for the glow plug start aid relay.

3. Switch the probes of the ohmmeter and measure the resistance from Test Point 2 to Test Point 1 on the harness connector for the relay.

Expected Result:

Both resistance measurements should be less than 10,000 Ohms.

Results:

• OK - Both resistance measurements are less than 10,000 Ohms. Reconnect the glow plug start aid relay. Proceed to Test Step 11.

• Not OK - One of the resistance measurements was more than 10,000 Ohms. The fault is in the relay coil.

  Repair: Perform the following repair:

  1. Install a replacement relay.

  2. Use the electronic service tool to perform the "Glow Plug Start Aid Override Test".

  3. Confirm that the fault has been eliminated.

  STOP

Test Step 11. Check the Fuse

1. Turn the battery disconnect switch to the OFF position.

2. Check the fuse for the glow plug start aid relay. Refer to Illustration 1.

Results:

• The fuse is blown. - There is a short in the power circuit for the glow plugs. Do not replace the fuse at this stage. Proceed to Test Step 12.

• The fuse is not blown - There may be an open circuit in the power circuit for the glow plugs. Proceed to Test Step 14.

Test Step 12. Disconnect the Relay and Check the Fuse

1. Disconnect the glow plug start aid relay.

2. Replace the fuse for the relay.

3. Turn the battery disconnect switch to the ON position. Wait for 5 seconds.

4. Turn the battery disconnect switch to the OFF position.

5. Check the fuse.

Results:

• The fuse is blown. - There is a short circuit in the wiring between the fuse and the glow plug start aid relay.

  Repair: Perform the following repair:

  1. Repair the faulty wiring or replace the faulty wiring. Replace the fuse. Reconnect the relay.

  2. Turn the battery disconnect switch to the ON position. Turn the keyswitch to the ON position.

  3. Use the electronic service tool to perform the "Glow Plug Start Aid Override Test".

  4. Confirm that the fault has been eliminated.

  STOP

• The fuse is not blown. - The wiring between the fuse and the relay is OK. Proceed to Test Step 13.

Test Step 13. Check the Wiring between the Relay and the Bus Bar for a Short Circuit

1. Disconnect the power supply wire from the bus bar.

2. Measure the resistance between Test Point B on the harness connector for the relay to a suitable ground.

Expected Result:

The resistance should be more than 10,000 Ohms.

Results:

• OK - The resistance is more than 10,000 Ohms. The wiring between the relay and the bus bar is not shorted. The fault is in the relay.

  Repair: Perform the following repair:

  1. Install a replacement relay. Reconnect the power supply wire to the bus bar.

  2. Turn the battery disconnect switch to the ON position. Turn the keyswitch to the ON position. Reconnect the relay.

  3. Use the electronic service tool to perform the "Glow Plug Start Aid Override Test".

  4. Confirm that the fault has been eliminated.

  STOP

• Not OK - The resistance is less than 10,000 Ohms. The wiring between the relay and the bus bar is shorted.

  Repair: Perform the following repair:

  1. Repair the faulty wiring or replace the faulty wiring. Reconnect the relay.

  2. Turn the battery disconnect switch to the ON position. Turn the keyswitch to the ON position.

  3. Use the electronic service tool to perform the "Glow Plug Start Aid Override Test".

  4. Confirm that the fault has been eliminated.

  STOP

Test Step 14. Check the Input Voltage to the Relay

1. Disconnect the connector for the glow plug start aid relay.

2. Turn the battery disconnect switch to the ON position.

3. Measure the voltage at Test Point A on the harness connector for the relay to a suitable ground.

Expected Result:

The measured voltage should be a constant 22.0 to 27.0 VDC.

Results:

• OK - The voltage is within the expected range. The wiring between the battery and the relay is OK. Leave the relay connector disconnected. Proceed to Test Step 15.

• Not OK - The voltage is not within the expected range. The fault is in the wiring between the battery and the relay.

  Repair: Perform the following repair:

  1. Repair the faulty wiring or replace the faulty wiring.

  2. Turn the keyswitch to the ON position. Reconnect the relay.

  3. Use the electronic service tool to perform the "Glow Plug Start Aid Override Test".

  4. Confirm that the fault has been eliminated.

  STOP

Test Step 15. Bypass the Relay

1. Turn the battery disconnect switch to the OFF position.

2. Fabricate an 8 AWG jumper wire that is 150 mm (6 inch) long.

3. Install the jumper wire between Test Point A and Test Point B on the harness connector for the relay.

4. Turn the battery disconnect switch to the ON position.

5. Use a clamp-on ammeter to measure the current on the power supply wire to the glow plugs.

6. Turn the battery disconnect switch to the OFF position.

7. Remove the jumper.

Expected Result:

The ammeter reading is approximately 4.5 Amps.

Results:

• The reading on the clamp-on ammeter is correct. - The fault is in the relay.

  Repair: Perform the following repair:

  1. Install a replacement relay.

  2. Turn the battery disconnect switch to the ON position. Turn the keyswitch to the ON position.

  3. Use the electronic service tool to perform the "Glow Plug Start Aid Override Test".

  4. Confirm that the fault has been eliminated.

  STOP

• The reading on the clamp-on ammeter is zero - The fault is in the wiring between the relay and the bus bar.

  Repair: Perform the following repair:

  1. Repair the faulty wiring or replace the faulty wiring. Reconnect the relay.

  2. Turn the battery disconnect switch to the ON position. Turn the keyswitch to the ON position.

  3. Use the electronic service tool to perform the "Glow Plug Start Aid Override Test".

  4. Confirm that the fault has been eliminated.

  STOP