Use this procedure to troubleshoot suspect problems with the circuits for the thermocouples.
This procedure covers the following diagnostic codes for the temperature sensors of the turbochargers:
- 1489-3 Left Turbo Turbine Outlet Temperature Sensor : Voltage Above Normal
- 1489-4 Left Turbo Turbine Outlet Temperature Sensor : Voltage Below Normal
- 1489-5 Left Turbo Turbine Outlet Temperature Sensor : Current Below Normal
- 1490-3 Right Turbo Turbine Outlet Temperature Sensor : Voltage Above Normal
- 1490-4 Right Turbo Turbine Outlet Temperature Sensor : Voltage Below Normal
- 1490-5 Right Turbo Turbine Outlet Temperature Sensor : Current Below Normal
- 1491-3 Right Turbo Turbine Inlet Temperature Sensor : Voltage Above Normal
- 1491-4 Right Turbo Turbine Inlet Temperature Sensor : Voltage Below Normal
- 1491-5 Right Turbo Turbine Inlet Temperature Sensor : Current Below Normal
- 1492-3 Left Turbo Turbine Inlet Temperature Sensor : Voltage Above Normal
- 1492-4 Left Turbo Turbine Inlet Temperature Sensor : Voltage Below Normal
- 1492-5 Left Turbo Turbine Inlet Temperature Sensor : Current Below Normal
This procedure covers the following diagnostic codes for the temperature sensors of the exhaust ports:
- 1531-3 Engine Cylinder #1 Exhaust Port Temperature Sensor : Voltage Above Normal
- 1531-4 Engine Cylinder #1 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1531-5 Engine Cylinder #1 Exhaust Port Temperature Sensor : Current Below Normal
- 1532-3 Engine Cylinder #2 Exhaust Port Temperature Sensor : Voltage Above Normal
- 1532-4 Engine Cylinder #2 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1532-5 Engine Cylinder #2 Exhaust Port Temperature Sensor : Current Below Normal
- 1533-3 Engine Cylinder #3 Exhaust Port Temperature Sensor : Voltage Above Normal
- 1533-4 Engine Cylinder #3 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1533-5 Engine Cylinder #3 Exhaust Port Temperature Sensor : Current Below Normal
- 1534-3 Engine Cylinder #4 Exhaust Port Temperature Sensor : Voltage Above Normal
- 1534-4 Engine Cylinder #4 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1534-5 Engine Cylinder #4 Exhaust Port Temperature Sensor : Current Below Normal
- 1535-3 Engine Cylinder #5 Exhaust Port Temperature Sensor : Voltage Above Normal
- 1535-4 Engine Cylinder #5 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1535-5 Engine Cylinder #5 Exhaust Port Temperature Sensor : Current Below Normal
- 1536-3 Engine Cylinder #6 Exhaust Port Temperature Sensor : Voltage Above Normal
- 1536-4 Engine Cylinder #6 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1536-5 Engine Cylinder #6 Exhaust Port Temperature Sensor : Current Below Normal
- 1537-3 Engine Cylinder #7 Exhaust Port Temperature Sensor : Voltage Above Normal
- 1537-4 Engine Cylinder #7 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1537-5 Engine Cylinder #7 Exhaust Port Temperature Sensor : Current Below Normal
- 1538-3 Engine Cylinder #8 Exhaust Port Temperature Sensor : Voltage Above Normal
- 1538-4 Engine Cylinder #8 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1538-5 Engine Cylinder #8 Exhaust Port Temperature Sensor : Current Below Normal
- 1539-3 Engine Cylinder #9 Exhaust Port Temperature sensor : Voltage Above Normal
- 1539-4 Engine Cylinder #9 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1539-5 Engine Cylinder #9 Exhaust Port Temperature Sensor : Current Below Normal
- 1540-3 Engine Cylinder #10 Exhaust Port Temperature Sensor : Voltage Above Normal
- 1540-4 Engine Cylinder #10 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1540-5 Engine Cylinder #10 Exhaust Port Temperature Sensor : Current Below Normal
- 1541-3 Engine Cylinder #11 Exhaust Port Temperature Sensor : Voltage Above Normal
- 1541-4 Engine Cylinder #11 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1541-5 Engine Cylinder #11 Exhaust Port Temperature Sensor : Current Below Normal
- 1542-3 Engine Cylinder #12 Exhaust Port Temperature Sensor : Voltage Above Normal
- 1542-4 Engine Cylinder #12 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1542-5 Engine Cylinder #12 Exhaust Port Temperature Sensor : Current Below Normal
- 1543-3 Engine Cylinder #13 Exhaust Port Temperature Sensor : Voltage Above Normal
- 1543-4 Engine Cylinder #13 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1543-5 Engine Cylinder #13 Exhaust Port Temperature Sensor : Current Below Normal
- 1544-3 Engine Cylinder #14 Exhaust Port Temperature Sensor : Voltage Above Normal
- 1544-4 Engine Cylinder #14 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1544-5 Engine Cylinder #14 Exhaust Port Temperature Sensor : Current Below Normal
- 1545-3 Engine Cylinder #15 Exhaust Port Temperature Sensor : Voltage Above Normal
- 1545-4 Engine Cylinder #15 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1545-5 Engine Cylinder #15 Exhaust Port Temperature Sensor : Current Below Normal
- 1546-3 Engine Cylinder #16 Exhaust Port Temperature Sensor : Voltage Above Normal
- 1546-4 Engine Cylinder #16 Exhaust Port Temperature Sensor : Voltage Below Normal
- 1546-5 Engine Cylinder #16 Exhaust Port Temperature Sensor : Current Below Normal
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 the Electronic Control Module (ECM) and by other modules. The temperatures can be viewed on Caterpillar Electronic Technician (ET).
The location of the ITSM depends on the configuration of the control system. The ITSM is located on the left rear corner of the engine if the engine is not equipped with an Auxiliary Sensing Module (ASM). The ITSM is located inside the terminal box if the engine is equipped with an ASM.
The ITSM generates an event code 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.
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| Illustration 1 | g01326149 |
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Schematic of the thermocouples for 1500 RPM engines that are not equipped with an ASM | |
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| Illustration 2 | g01326152 |
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Schematic of the thermocouples for 1500 RPM engines that are equipped with an ASM | |
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| Illustration 3 | g01326161 |
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Schematic of the thermocouples for the 1800 RPM engines | |
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| Illustration 4 | g01235269 |
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Schematic for the electrical power to the ITSM The engine is not equipped with an Auxiliary Sensing Module (ASM). | |
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| Illustration 5 | g01302572 |
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Schematic for the electrical power to the ITSM The engine is equipped with an Auxiliary Sensing Module (ASM). | |
Test Step 1. Inspect the Electrical Connectors and Wiring
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Note: For the following steps, refer to Troubleshooting, "Electrical Connectors - Inspect".
- Thoroughly inspect each of the following connectors:
- ECMJ1/P1 connectors
- J7/P7 and J9/P9 connectors on the terminal box
- Check the torque of the allen head screw for the ECM connectors.
- 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.
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
- Access the "Active Diagnostic" screen for the ITSM on Cat ET. Determine if any of the following diagnostic codes for the thermocouples are active:
- 1489-3 through 1492-3 (voltage above normal)
- 1489-4 through 1492-4 (voltage below normal)
- 1489-5 through 1492-5 (current below normal)
- 1531-3 through 1546-3 (voltage above normal)
- 1531-4 through 1546-4 (voltage below normal)
- 1531-5 through 1546-5 (current below normal)
- 1042-9 ("Unable to communicate")
Expected Result:
None of the above diagnostic codes for the thermocouples 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, "Symptom Troubleshooting".
STOP
- Active "voltage below normal" or "voltage above normal" - At least one "voltage below normal" or "voltage above normal" diagnostic code is active. Proceed to Test Step 3.
- Active "current below normal" - At least one "current below normal" diagnostic code is active. Proceed to Test Step 4.
- Active 1042-9 code - The ECM cannot communicate with the ITSM. Proceed to Test Step 6.
Test Step 3. Create an Open Circuit
- Disconnect the connector for the thermocouple with the "voltage below normal" diagnostic code.
- 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 "current below normal" diagnostic code for the disconnected thermocouple.
Results:
- Yes - There is an active "current below normal" diagnostic code for the disconnected thermocouple. The ITSM and the harness are OK.
Repair: Perform the following procedure:
- Thoroughly inspect the thermocouple's connectors. Ensure that the connectors and the seals are in good condition.
- Connect the thermocouple's connectors and check for an active "voltage below normal" diagnostic code.
If the "voltage below normal" diagnostic code becomes active again, there is a problem with the thermocouple.
- Disconnect the suspect thermocouple and connect a thermocouple that is known to be good. Do not install the thermocouple into the engine yet.
- Check for an active "voltage below normal" diagnostic code.
If the diagnostic code is not generated with the good thermocouple, remove the suspect thermocouple from the engine. Install the good thermocouple.
- Clear the logged diagnostic codes.
STOP
- No - There is not an active "current below normal" 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
- Disconnect the connector for the thermocouple with the "current below normal" diagnostic code.
- Install a jumper wire into terminals A and B on the harness connector for the suspect thermocouple.
- 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.
- 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 "voltage below normal" diagnostic code was generated. When the jumper wire was removed, the "current below normal" diagnostic code recurred.
Results:
- Yes - When the jumper wire was installed, a "voltage below normal" diagnostic code was generated. When the jumper wire was removed, the "current below normal" diagnostic code recurred. The ITSM and the harness are OK.
Repair: Perform the following procedure:
- Thoroughly inspect the thermocouple's connectors. Ensure that the connectors and the seals are in good condition.
- Connect the thermocouple's connectors and check for an active "current below normal" diagnostic code.
If the "current below normal" diagnostic code becomes active again, there is a problem with the thermocouple.
- Disconnect the suspect thermocouple and connect a thermocouple that is known to be good. Do not install the good thermocouple into the engine yet.
- Check for an active "current below normal" diagnostic code.
If the diagnostic code is not generated with the good thermocouple, remove the suspect thermocouple from the engine. Install the good thermocouple.
- Clear the logged diagnostic codes.
STOP
- No - When the jumper wire was installed, the "current below normal" 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
- Disconnect the 54-pin connector from the ITSM. Thoroughly inspect the 54-pin connectors. Ensure that the connectors are in good condition.
Note: When the 54-pin connectors are disconnected, an active "current below normal" diagnostic code will be generated for all of the thermocouples. This is normal. Only pay attention to the diagnostic codes for the suspect thermocouple.
- 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.
- Install a jumper wire into the terminals for the suspect sensor on the 54-pin connector on the ITSM. For identification of the terminals, refer to Illustration 1 or 3.
- Observe the "Active Diagnostic" screen. Allow a minimum of 30 seconds for any diagnostic codes to be generated.
Expected Result:
When the 54-pin connectors were disconnected, an "current below normal" diagnostic code was generated for the suspect sensor. When the jumper wire was installed, a "voltage below normal" diagnostic code was generated.
Results:
- Yes - When the 54-pin connectors were disconnected, an "current below normal" diagnostic code was generated for the suspect sensor. When the jumper wire was installed, a "voltage below normal" 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 in order to ensure reliable operation. 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 54-pin connectors were disconnected, an "current below normal" diagnostic code was not generated for the suspect sensor. When the jumper wire was installed, a "voltage below normal" diagnostic code was not generated. There may be a problem with the ITSM.
Repair: Perform the following steps:
- Remove the jumper wire from the connector on the ITSM.
- Temporarily install a new ITSM. Refer to Troubleshooting, "Control Module - Replace".
- If the problem is resolved with the new ITSM, install the original ITSM and verify that the problem returns. If the new ITSM operates correctly and the original ITSM does not operate correctly, replace the original ITSM. Refer to Troubleshooting, "Control Module - Replace".
STOP
Test Step 6. Check for Electrical Power at the ITSM
- Refer to Illustration 6. Measure the voltage at the junction box.
- Disconnect the P18 connector from the ITSM.
Show/hide table
Illustration 7 g01233703 Locations for the voltage check at the harness connector - Measure the voltage between terminals N and P at the harness connector.
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| Illustration 6 | g01302546 |
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Location for the voltage check at the junction box | |
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 - Test".
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