The Engine Control Module (ECM) monitors the following parameters in order to calculate an exhaust temperature:
- Barometric pressure
- Intake manifold air temperature
- Engine speed
Certain operating conditions may cause the calculated exhaust temperature to increase to a level that may damage engine components. If a high exhaust temperature occurs, the ECM derates the engine in order to reduce the calculated exhaust temperature. The engine is derated only to a level that allows the calculated exhaust temperature to return to an acceptable level.
| Associated Diagnostic Trouble Codes | ||
| J1939 Code | CDL Code | |
| 108-3 | 274-3 | |
| 108-4 | 274-4 | |
| 108-13 | 274-13 | |
Note: Cat ET will report the status for atmospheric pressure as the ambient barometric pressure. The readings for the turbocharger inlet pressure sensor will be approximately the same value that is reported by the atmospheric pressure sensor. The approximate same value readings will occur while the engine is not running. If the readings do not agree, troubleshoot the sensor circuit for the suspect sensor. Refer to Troubleshooting, “Sensor Signal (Analog, Active) – Test”.
Probable Causes
- Associated codes
- Boost Leak
- Engine operating conditions
- Failed exhaust balance valve
- High altitude
- Obstructed aftercooler
| Troubleshooting Test Steps | Values | Results |
|---|---|---|
| 1. Check for Associated Diagnostic CodesA. Establish communication between Caterpillar Electronic Technician (ET) and the ECM. Refer to Troubleshooting, “Electronic Service Tools”, if necessary.
B. Determine if a code is active or logged. |
Associated diagnostic codes | Result: An associated diagnostic code is active or logged.Troubleshoot the associated code. Refer to Troubleshooting, “Diagnostic Trouble Codes” in order to troubleshoot the associated diagnostic code.
Result: An associated diagnostic code is not active or logged. Proceed to Test Step 2. |
| DTC with associated derate? | Data logged in this histogram? | Interpretation |
| No | Yes | Derate was probably caused by the exhaust temperature derate. |
| Yes | Yes | There may be multiple causes for derate since this exhaust temperature histogram only logs data when it has the largest derate ( another derate may have been active due to a diagnostic trouble code, but a larger exhaust temperature derate was applied). |
| Yes | No | Derate was probably not caused by the exhaust temperature derate. |
Illustration 1 g02475817
Example of Cat ET screenshot of the histogram. This histogram is populated when the engine system has calculated a condition in which high exhaust temperatures are present. A fault code will not be logged when the system calculates a high exhaust temperature condition, but will activate a de-rate to the engine in order to protect the engine system. This is normal under most circumstances and no additional troubleshooting is necessary.
Note: Information from this histogram is to be used with active and logged diagnostic trouble codes. This histogram is informational if no diagnostic codes are active or logged.
| Troubleshooting Test Steps | Values | Results |
|---|---|---|
|
2. Check for Boost Leakage
A. Apply a light load to the engine and check for boost leakage. |
Boost leaks |
Result: Boost leakage was found.
Repair the leaks. Return the unit to service. Result: Boost leakage was not found. Proceed to Test Step 3. |
|
3. Check the Engine Operating Conditions
A. Check the histogram to determine if the high exhaust temperature was due to normal operation. If derates are suspected, reset histogram and return the unit to service. If the histogram repopulates without fault codes, the derate was under normal engine operation. |
Normal operation |
Result: The code was logged during a heavy load.
Reduce the load on the engine. Return the unit to service. Result: The code was not logged during a heavy load. Proceed to Test Step 4. |
|
4. Check the Exhaust Balance Valve
A. An exhaust balance valve that has failed in the closed position can cause high exhaust temperatures, Refer to Troubleshooting, “Exhaust Balance Valve – Test” for the correct troubleshooting procedure. |
Failed exhaust balance valve |
Result: The exhaust balance valve has failed.
Repair or replace the balance valve. Return the unit to service. Result: The exhaust balance valve has not failed. Proceed to Test Step 5. |
|
5. Check the Engine Operating Altitude
A. Check the engine operating altitude. High altitudes can cause high exhaust temperatures, consider the operational altitude when troubleshooting a high exhaust temperature. High exhaust temperatures are associated with high operational altitudes. When operating below 5500ft and the ambient temperature is below |
High operational altitudes |
Result: The engine was operating at high altitudes.
The high exhaust temperature was due to high altitudes. Return the unit to service. Result: The engine was not operating at high altitudes. Proceed to Test Step 6. |
|
6. Check for an Obstructed Aftercooler
A. The intake manifold air temperature can increase if the flow through the aftercooler is obstructed. Check the aftercooler for obstructions or debris. Ensure that the flow of air or coolant through the aftercooler is adequate. |
Obstructed aftercooler |
Result: The engine aftercooler was obstructed.
Clear any obstructions. Return the unit to service. |
Complete the procedure in the order in which the steps are listed.
The procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).