G3520B Industrial Engine Caterpillar

The Integrated Temperature Sensing Module (ITSM) monitors type K thermocouples at each cylinder exhaust port and at the inlets and outlets for both turbochargers. The ITSM can also calculate the average temperature for each cylinder bank (left and right). Temperature readings of the thermocouples are available over the Cat Data Link for use by each Electronic Control Module (ECM) and by other modules. The temperatures can be viewed on the Caterpillar Electronic Technician (ET).

The ITSM generates event codes for each of the following programmable conditions:

• High exhaust temperature

• High deviation of an exhaust port temperature

• Low deviation of an exhaust port temperature

• High inlet temperature to the turbocharger turbine

• High outlet temperature from the turbocharger turbine

A diagnostic code is generated by the ITSM for the circuit of any thermocouple that is shorted to the +Battery side, shorted to ground, or open.

Logged diagnostic codes provide a historical record. Before you begin this procedure, use Cat ET to print the logged codes to a file.

This troubleshooting procedure may generate additional diagnostic codes. Keep your mind on correcting the cause of the original diagnostic code. Clear the diagnostic codes after the problem is resolved.

Illustration 1	g01233940
Schematic of the circuits for the thermocouples

Illustration 2	g01233959
Schematic for the electrical power to the ITSM

Test Step 1. Inspect the Electrical Connectors and Wiring

1. Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.

Note: For the following steps, refer to Troubleshooting, "Inspecting Electrical Connectors".

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Illustration 3	g01090253
Terminal box for the master ECM (1) J1/P1 connectors for the master ECM (2) J8/P8 connectors for the harness to the ITSM

2. Thoroughly inspect each of the following connectors:
   • Master ECM J1/P1 connectors

   • J8/P8 connectors on the terminal box for the master ECM

   1. Check the torque of the allen head screw for the ECM connectors. Refer to Troubleshooting, "Inspecting Electrical Connectors" for the correct torque.
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   Illustration 4	g00995272
   Harness side of the P1 connector (P1-8) Cat Data Link + (P1-9) Cat Data Link −

   2. Perform a 45 N (10 lb) pull test on each of the wires that are associated with the circuit for the ITSM.
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   Illustration 5	g01090268
   Left side view (3) Thermocouple for the temperature of the cylinder's exhaust (4) Thermocouple for the temperature of the exhaust at the inlet of the turbocharger (5) Thermocouple for the temperature of the exhaust at the outlet of the turbocharger

   3. Carefully inspect the connectors for each of the thermocouples. Check the harnesses and wiring for abrasion and for pinch points from each thermocouple to the ITSM.
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   Illustration 6	g01090277
   Front view (6) ITSM (7) J18/P18 connectors for the harness to the terminal box for the master ECM (8) J40/P40 connectors for the harness to the thermocouples

   4. Thoroughly inspect the J18/P18 connectors and the J40/P40 connectors for the ITSM. Check the harnesses and wiring for abrasion and for pinch points from the ITSM to the master ECM.

Expected Result:

All of the connectors, pins, and sockets are connected properly. The connectors and the wiring do not have corrosion, abrasion, or pinch points.

Results:

• OK - The components are in good condition with proper connections. Proceed to Test Step 2.

• Not OK - The components are not in good condition and/or at least one connection is improper.

  Repair: Perform the necessary repairs and/or replace parts, if necessary. If the wiring harness from the thermocouples to the ITSM requires repair, replace the harness in order to ensure reliable operation.All of the wiring from the thermocouples to the ITSM must be type K. The polarity of the wires from each thermocouple to the ITSM must be maintained in order for the ITSM to read the correct temperatures.

  STOP

Test Step 2. Verify the Active Diagnostic Codes

1. Access the "Active Diagnostic" screen for the ITSM on Cat ET. Determine if any of the following diagnostic codes for the thermocouples are active:
   • 1489-03 through 1492-03 ("short to +batt")

   • 1489-04 through 1492-04 ("short to ground")

   • 1489-05 through 1492-05 ("open circuit")

   • 1531-03 through 1550-03 ("short to +batt")

   • 1531-04 through 1550-04 ("short to ground")

   • 1531-05 through 1550-05 ("open circuit")

   • 1042-09 ("Unable to communicate")

Expected Result:

None of the above diagnostic codes are active.

Results:

• No Active Codes - None of the above diagnostic codes are active.

  Repair: If any of the codes are logged, there may be an intermittent condition that is causing the codes to be generated. If the engine is not running properly, refer to Troubleshooting, "Troubleshooting Without a Diagnostic Code".

  STOP

• Active "short to ground" or "short to +batt" - At least one "short to ground" or "short to +batt" diagnostic code is active. Proceed to Test Step 3.

• Active "open circuit" - At least one "open circuit" diagnostic code is active. Proceed to Test Step 4.

• Active 1042-09 code - The master ECM cannot communicate with the ITSM. Proceed to Test Step 6.

Test Step 3. Create an Open Circuit

1. Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.

2. Disconnect the connector for the thermocouple with the short circuit diagnostic code.

3. Restore the electrical power to the engine. Set the engine control to the STOP mode.

4. Access the "Active Diagnostic" screen for the ITSM on Cat ET. Allow a minimum of 30 seconds for any diagnostic codes to be generated.

Expected Result:

There is an active "open circuit" diagnostic code for the disconnected thermocouple.

Results:

• Yes - There is an active "open circuit" diagnostic code for the disconnected thermocouple. The ITSM and the harness are OK.

  Repair: Perform the following procedure:

  1. Thoroughly inspect the thermocouple's connectors. Ensure that the connectors and the seals are in good condition.

  2. Connect the thermocouple's connectors and check for an active short circuit diagnostic code.

     If the short circuit diagnostic code becomes active again, there is a problem with the thermocouple.

  3. Disconnect the suspect thermocouple and connect a thermocouple that is known to be good. Do not install the thermocouple into the engine yet.

  4. Check for an active short circuit diagnostic code.

     If the diagnostic code is not generated with the good thermocouple, remove the suspect thermocouple from the engine. Install the good thermocouple.

  5. Clear the logged diagnostic codes.

  STOP

• No - There is not an active "open circuit" diagnostic code for the disconnected thermocouple. There is a short circuit between the harness for the thermocouple and the ITSM. Proceed to Test Step 5.

Test Step 4. Create a Short Circuit

1. Fabricate a jumper wire that is approximately 100 to 150 mm (4 to 6 inches) long with Deutsch terminals on both ends.

2. Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.

3. Disconnect the connector for the thermocouple with the open circuit diagnostic code.

4. Install the jumper wire into terminals A and B on the harness connector for the suspect thermocouple.

5. Restore the electrical power to the engine. Set the engine control to the STOP mode.

6. Access the "Active Diagnostic" screen for the ITSM on Cat ET. Allow a minimum of 30 seconds for any diagnostic codes to be generated. Observe the "Active Diagnostic" screen.

7. Remove the jumper wire and observe the "Active Diagnostic" screen. Allow a minimum of 30 seconds for any diagnostic codes to be generated.

Expected Result:

When the jumper wire was installed, a "short circuit" diagnostic code was generated. When the jumper wire was removed, the "open circuit" diagnostic code recurred.

Results:

• Yes - When the jumper wire was installed, a "short circuit" diagnostic code was generated. When the jumper wire was removed, the "open circuit" diagnostic code recurred. The ITSM and the harness are OK.

  Repair: Perform the following procedure:

  1. Thoroughly inspect the thermocouple's connectors. Ensure that the connectors and the seals are in good condition.

  2. Connect the thermocouple's connectors and check for an active open circuit diagnostic code.

     If the open circuit diagnostic code becomes active again, there is a problem with the thermocouple.

  3. Disconnect the suspect thermocouple and connect a thermocouple that is known to be good. Do not install the good thermocouple into the engine yet.

  4. Check for an active open circuit diagnostic code.

     If the diagnostic code is not generated with the good thermocouple, remove the suspect thermocouple from the engine. Install the good thermocouple.

  5. Clear the logged diagnostic codes.

  STOP

• No - When the jumper wire was installed, the "open circuit" diagnostic code recurred. There is probably an open circuit in the harness between the ITSM and the connector for the thermocouple.

  Repair: Remove the jumper wire.

  Proceed to Test Step 5.

Test Step 5. Check the ITSM

1. Fabricate a jumper wire that is approximately 100 to 150 mm (4 to 6 inches) long with Deutsch terminals on both ends.

2. Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.

3. Disconnect the P40 plug from the ITSM. Thoroughly inspect the J40/P40 connectors. Ensure that the connectors are in good condition.

4. Restore the electrical power to the engine. Set the engine control to the STOP mode.

Note: When the J40/P40 connectors are disconnected, an active "open circuit" diagnostic code will be generated for all of the thermocouples. This is normal. Only pay attention to the diagnostic codes for the suspect thermocouple.

5. Access the "Active Diagnostic" screen for the ITSM on Cat ET. Allow a minimum of 30 seconds for any diagnostic codes to be generated. Observe the "Active Diagnostic" screen.

6. Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.

7. Install the jumper wire into the terminals for the suspect thermocouple on the J40 connector. For identification of the terminals, refer to Illustration 1.

8. Restore the electrical power to the engine. Set the engine control to the STOP mode. Observe the "Active Diagnostic" screen. Allow a minimum of 30 seconds for any diagnostic codes to be generated.

Expected Result:

When the J40/P40 connectors were disconnected, an "open circuit" diagnostic code was generated for the suspect thermocouple. When the jumper wire was installed, a "short circuit" diagnostic code was generated.

Results:

• Yes - When the J40/P40 connectors were disconnected, an "open circuit" diagnostic code was generated for the suspect thermocouple. When the jumper wire was installed, a "short circuit" diagnostic code was generated. The ITSM is OK. There is a problem in the harness between the ITSM and the connector for the suspect thermocouple.

  Repair: Remove the jumper wire. Replace the harness. Clear the logged diagnostic codes and verify that the problem is resolved.All of the wiring from the thermocouples to the ITSM must be type K. The polarity of the wires from each thermocouple to the ITSM must be maintained in order for the ITSM to read the correct temperatures.

  STOP

• No - Either of the following results or both of the results occurred: When the J40/P40 connectors were disconnected, an "open circuit" diagnostic code was not generated for the suspect thermocouple. When the jumper wire was installed, a "short circuit" diagnostic code was not generated.

  Repair: Perform the following procedure:

  1. Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.

  2. Remove the jumper wire. Disconnect the P18 connector from the ITSM.

  3. Connect an ITSM that is known to be good to the P18 plug from the terminal box. Connect the P40 plug to the good ITSM. Make sure that the good ITSM has the correct flash programming. Refer to Troubleshooting, "Replacing the ITSM".

  4. Restore the electrical power to the engine. Set the engine control to the STOP mode. Observe the "Active Diagnostic" screen. Allow a minimum of 30 seconds for any diagnostic codes to be generated.

  5. Verify that no diagnostic codes are generated with the good ITSM.

  6. Set the engine control to the OFF/RESET mode. Remove the electrical power from the engine.

  7. Connect the original ITSM to the P18 plug from the terminal box. Connect the P40 plug to the original ITSM.

  8. Verify that the diagnostic code recurs with the original ITSM.

  9. Replace the ITSM. See Troubleshooting, "Replacing the ITSM".

  STOP

Test Step 6. Check for Electrical Power at the ITSM

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Illustration 7	g01233966
Location for the voltage check at the junction box

1. Refer to Illustration 7. Measure the voltage for the ITSM at the junction box.

2. Disconnect the P18 connector from the ITSM.

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Illustration 8	g01233703
Locations for the voltage check at the harness connector

3. Measure the voltage between terminals N and P at the harness connector.

Expected Result:

The voltage at the harness connector is within two volts of the voltage at the junction box.

Results:

• Yes - The voltage at the harness connector is within two volts of the voltage at the junction box. The actuator is receiving the proper operating voltage.

  Repair: Refer to Troubleshooting, "Cat Data Link".

  STOP

• No - The voltage at the harness connector is not within two volts of the voltage at the junction box. The actuator is not receiving the proper operating voltage.

  Repair: Determine the cause of the excessive voltage drop. Make the necessary repairs.

  STOP