C7 and C9 Industrial Engines Troubleshooting – Exhaust Temperature Is High

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.

Table 1
Associated Diagnostic Trouble Codes
J1939 Code	CDL Code
108-3	274-3
108-4	274-4

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
High altitude
Obstructed aftercooler

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.

Recommended Actions

Table 2
Troubleshooting Test Steps	Values	Results
1. Check for Associated Diagnostic CodesA. Establish communication between Cat® 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.Repair: 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.

Table 3
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.

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.

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.

Table 4
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: 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. When possible, interview the operator. Determine if the engine is being operated under heavy load. Ensure that the engine is being operated at the proper engine speed. 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. Repair: 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 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 30° C (85° F), altitude should not cause a high exhaust temperature derate.	High operational altitudes	Result: The engine was operating at high altitudes. Repair: 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 5.
5. 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. Repair: Clear any obstructions. Return the unit to service.

Probable Causes

Recommended Actions

Leave a Reply Cancel reply