G3500 Industrial Engines Caterpillar

The Timing Control Module (TCM) requires a DC power source for operation. The TCM provides the regulated voltages in order to power the sensors.

The power source must be capable of providing an instantaneous supply of 16 amperes at a minimum of 18 VDC. An insufficient voltage supply at powerup may cause the TCM to operate improperly.

The power source must supply 3 amperes at a minimum of 18 VDC after the initial powerup.

The +battery voltage is carried by the engine harness from the power distribution box to the engine mounted junction box. The voltage is fused to 15 amperes and then carried to the remote control panel by the extension harness.

The +battery voltage is connected to the Status Control Module (SCM) and the Engine Control Switch (ECS) in the remote control panel. The ECS switches the control of +battery to the TCM and the DDT. The extension harness connects +battery to the TCM.

The -battery signal is carried by the engine harness from the power distribution box to the junction box. The junction box and the engine harness connect the -battery to the TCM and the DDT from the control panel.

The extension harness connects -battery from the engine mounted junction box to the remote control panel for distribution to the status control and the DDT.

Test Step 1. Check for Connector Damage.

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There is a strong electrical shock hazard unless the system power is disconnected. Use extreme caution when examine the battery source.

1. Remove the power from the control system.

2. Turn the ECS to the OFF/RESET position.

3. Open the circuit breaker for the fuse in the engine mounted junction box.

4. Inspect the following components for damage, corrosion or loose connections: TCM, battery posts, power distribution box, junction box, remote control panel and alternator. Refer to Troubleshooting, "Inspecting Electrical Connectors".

5. Inspect the battery connections for the correct polarity.

Expected Result:

The components are free of damage, corrosion, and/or incorrect attachments. The battery connections are correct.

Results:

• OK - The components are in good condition. Proceed to test step 2.

• Not OK - The components require service.

  Repair: Repair the components or wiring and/or replace the components or wiring.

  Stop.

Test Step 2. Check the Fuse for the Timing Control.

1. Remove the 15 amp fuse from the breaker in the engine mounted junction box.

2. Use the 400 ohm scale to measure the resistance of the fuse.

Expected Result:

The resistance is less than 2 ohms.

Results:

• OK - The fuse is OK. The supply does not have a short circuit. Proceed to test step 3.

• Not OK - There is a problem with the fuse. Proceed to test step 4.

Test Step 3. Check for an Open Circuit.

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Disconnect the power supply source (Battery) from the electrical system at the power distribution box or the power source. Failure to do so will create a severe electrical shock hazard and may damage electrical measuring equipment.

1. Remove power from the control system.

2. Turn the Engine Control Switch (ECS) to the OFF/RESET position.

3. Open the circuit breaker for the fuse in the engine mounted junction box.

4. Remove the 15 amp fuse from the circuit breaker in the engine mounted junction box.

Note: Refer to the engine's wiring schematic for the actual wiring.

5. Use the 400 ohm scale on the multimeter to measure the resistance between the points that are listed in Table 1:
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   Table 1

   Points To Check For an Open Circuit
   Terminal strip in the engine mounted junction box	+battery terminal at the Status Control Module (SCM)
   +battery terminal at the SCM	Terminal 6 at the ECS
   Terminal strip in the engine mounted junction box	-battery terminal at the SCM
   Terminal strips in the engine mounted junction box
   Terminal strips in the remote control panel
   Terminal strip in the engine mounted junction box	Terminal 10 for the ECS
   	Pin M at the connector for the Timing Control Module (TCM)
   	Pin N at the connector for the TCM
   	Pin A at the connector for the DDT in the engine mounted junction box
   	Pin B at the connector for the DDT in the engine mounted junction box
   	Pin A at the connector for the DDT in the remote control panel
   	Pin B at the connector for the DDT in the remote control panel

Expected Result:

The resistance is less than 2 ohms.

Results:

• OK - The wiring is OK. Proceed to test step 5.

• Not OK - There is a problem in the wiring.

  Repair: Install the fuse. Repair the components or wiring and/or replace the components or wiring.

  Stop.

Test Step 4. Check for a Short Circuit.

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Disconnect the power supply source (Battery) from the electrical system at the power distribution box or the power source. Failure to do so will create a severe electrical shock hazard and may damage electrical measuring equipment.

1. Disconnect the TCM.

2. Disconnect the DDT.

3. Set the multimeter to the 4000 ohm scale. Measure the resistance at the terminal strips with the +battery to terminal strips that do not have the +battery.

4. Measure the resistance at the terminal strips from the +battery to the engine block.

5. Measure the resistance at the terminal strips from the -battery to the terminal strips that do not have the -battery.

Expected Result:

The resistance is greater than 2000 ohms.

Results:

• OK - The resistance is correct. Proceed to test step 6.

• Not OK - A short circuit is present in the wiring.

  Repair: Replace the fuse. Repair the connectors or wiring and/or replace the connectors or wiring.

  Stop.

Test Step 5. Check the ECS for an Open Circuit.

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Disconnect the power supply source (Battery) from the electrical system at the power distribution box or the power source. Failure to do so will create a severe electrical shock hazard and may damage electrical measuring equipment.

1. Remove power from the control system.

2. Turn the ECS to the OFF/RESET position.

3. Remove the 15 amp fuse from the circuit breaker in the engine mounted junction box.

4. Set the multimeter to the 400 ohm scale. Measure the resistance between the +battery terminal of the SCM to the engine mounted junction box on the other side of the ECS.

   Note: Refer to your engine schematic for this terminal, which is connected to terminal 7 at the ECS.

5. Measure the resistance between the -battery terminal of the SCM and terminal 10 of the SCM.

6. Turn the ECS to the STOP position.

7. Measure the resistance between the +battery terminal of the SCM to the engine mounted junction box on the other side of the ECS.

   Note: Refer to your engine schematic for this terminal, which is connected to terminal 10 at the ECS.

8. Measure the resistance between the -battery terminal of the SCM and terminal 10 of the SCM.

9. Turn the ECS to the AUTO position.

10. Measure the resistance between the +battery terminal of the SCM to the engine mounted junction box on the other side of the ECS.

    Note: Refer to your engine schematic for this terminal, which is connected to terminal 8 at the ECS.

11. Measure the resistance between the -battery terminal of the SCM and terminal 11 of the SCM.

12. Turn the ECS to the MANUAL position.

13. Measure the resistance between the +battery terminal of the SCM to the engine mounted junction box on the other side of the ECS.

    Note: Refer to your engine schematic for this terminal, which is connected to terminal 9 at the ECS.

14. Measure the resistance between the -battery terminal of the SCM and terminal 9 of the SCM.

Expected Result:

The resistance is less than 2 ohms.

Results:

• OK - The resistance is correct. Proceed to test step 7.

• Not OK - The ECS has failed or the wiring from the switch has failed.

  Repair: Inspect the wiring for an open circuit. If no open circuits are found replace the ECS.

  Stop.

Test Step 6. Check the TCM for a Short Circuit.

1. Set the multimeter to the 4000 ohm scale. Measure the resistance between pin M and pin N of the TCM.

Expected Result:

The resistance is greater than 2000 ohms.

Results:

• OK - The resistance is correct. Proceed to test step 8.

• Not OK - The TCM has failed.

  Repair: Replace the TCM. Program the new TCM. Refer to Troubleshooting, "Programming the TCM".

  Stop.

Test Step 7. Check the Polarity of the Battery.

1. Install the 15 amp fuse into the circuit breaker in the engine mounted junction box.

2. Set the multimeter to the 40 VDC scale. Measure the voltage across the terminal strips for the +battery and the -battery in the engine mounted junction box. Connect the "COM" terminal of the multimeter to the -battery terminal strip.

Expected Result:

The voltage is positive.

Results:

• OK - The polarity is correct. Proceed to test step 9.

• Not OK - The polarity is reversed.

  Repair: Properly connect the battery. Reset the system and troubleshoot any faults.

  Stop.

Test Step 8. Check the ECS for a Short Circuit.

1. Turn the ECS to the STOP position.

2. Set the multimeter to the 4000 ohm scale. Measure the resistance in the engine mounted junction box from the +battery terminal strip to the -battery terminal strip.

3. Turn the ECS to the MANUAL position.

4. Measure the resistance in the engine mounted junction box from the +battery terminal strip to the -battery terminal strip.

5. Turn the ECS to the AUTO position.

6. Measure the resistance in the engine mounted junction box from the +battery terminal strip to the -battery terminal strip.

Expected Result:

The resistance is greater than 2000 ohms.

Results:

• OK - The resistance is correct. Proceed to test step 10.

• Not OK - The ECS has a wiring problem.

  Repair: Repair the wiring or replace the switch.

  Stop.

Test Step 9. Check the Voltage.

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There is a strong electrical shock hazard unless the system power is disconnected. Use care when you are handling the probes to make the measurement across the battery positive and the battery ground lines. Shorting the lines will create a strong electrical arc and shock hazard.

1. Install the 15 amp fuse into the circuit breaker in the engine mounted junction box.

2. Close the breaker.

3. Turn the ECS to the OFF/RESET position.

4. Connect the TCM to the engine harness.

5. Disconnect the DDT from the engine mounted junction box.

6. Disconnect the harness for the DDT from the engine mounted junction box.

7. Do not apply power to the TCM or the DDT.

8. Set the multimeter to the 40 VDC scale. Measure the voltage at the terminal strips for the battery in the remote control panel.

9. Turn the ECS to the STOP position.

10. Measure the voltage at the terminal strips for the battery in the remote control panel.

Expected Result:

The voltage is greater than 18 VDC.

Results:

• OK - The voltage is correct. Proceed to test step 11.

• Not OK - The battery has failed.

  Repair: Charge the battery or replace the battery.

  Stop.

Test Step 10. Check the DDT and the Harness of the DDT for a Short Circuit.

1. Connect the DDT to the engine mounted junction box. See Troubleshooting, "Connecting the DDT to the TCM".

2. Set the multimeter to the 4000 ohm scale. Measure the resistance in the engine mounted junction box from the +battery terminal strip to the -battery terminal strip.

Expected Result:

The resistance is greater than 2000 ohms.

Results:

• OK - The short circuit is not caused by the DDT or the harness. Proceed to test step 12.

• Not OK - The DDT or the harness has failed.

  Repair: Repair the DDT or the harness and/or replace the DDT or the harness.

  Stop.

Test Step 11. Check the Voltage at the TCM.

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There is a strong electrical shock hazard unless the system power is disconnected. Use care when you are handling the probes to make the measurement across the battery positive and the battery ground lines. Shorting the lines will create a strong electrical arc and shock hazard.

1. Turn the ECS to the OFF/RESET position.

2. Disconnect the TCM from the engine harness.

3. Turn the ECS to the STOP position.

4. Set the multimeter to the 40 VDC scale. Connect the "COM" terminal of the multimeter to pin N. Measure the voltage of the connector for the TCM on the engine harness from pin M to pin N.

Expected Result:

The voltage is greater than 18 VDC.

Results:

• OK - The voltage is correct. Proceed to test step 13.

• Not OK - The voltage is not correct.

  Repair: If the voltage is between 0 and 18, recharge the battery or replace the battery. If the voltage is 0, there is a problem in the wiring harness. Repair the connectors or wiring and/or replace the connectors or wiring.

  Stop.

Test Step 12. Check for Short Circuit

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Disconnect the power supply source (Battery) from the electrical system at the power distribution box or the power source. Failure to do so will create a severe electrical shock hazard and may damage electrical measuring equipment.

1. Remove the 15 amp fuse from the circuit breaker in the engine mounted junction box.

Note: Refer to the engine wiring diagram for the actual engine wiring.

2. Set the multimeter to the 4000 ohm scale. Measure the resistance in the engine mounted junction box from the -battery terminal strips to all of the other terminals which are not connected to the -battery.

   Note: The system may not have a -battery that is connected to the engine block. Measure the resistance from the engine block to all of the terminals that are not connected to the -battery.

Expected Result:

The resistance is greater than 2000 ohms.

Results:

• OK - No short circuit was found.

  Repair: If the following components are connected to the power supply for the SCM, check these components: motor, gas valve and actuator.

  Stop.

• Not OK - A short circuit is found.

  Repair: Note the terminal strips which indicate a short circuit. Install the fuse. Repair the connectors or wiring and/or replace the connectors or wiring.

  Stop.

Test Step 13. Check the Voltage at the DDT.

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There is a strong electrical shock hazard unless the system power is disconnected. Use care when you are handling the probes to make the measurement across the battery positive and the battery ground lines. Shorting the lines will create a strong electrical arc and shock hazard.

1. Turn the ECS to the OFF/RESET position.

2. Connect the DDT to the engine mounted junction box.

3. Turn the ECS to the STOP position.

4. Set the multimeter to the 40 VDC scale. Measure the voltage at the harness for the DDT.

5. Connect the "COM" terminal of the multimeter to pin 2. Measure the voltage from pin 1 to pin 2.

Expected Result:

The voltage is greater than 18 VDC.

Results:

• OK - The voltage is correct.

  Repair: Check the bulb that indicates power. Check the wiring.

  Stop.

• Not OK -

  Repair: If the voltage is between 0 and 18, recharge the battery or replace the battery. If the voltage is 0 VDC there is a problem in the wiring harness. Repair the connectors or wiring and/or replace the connectors or wiring.

  Stop.