Diagnostic article Generic OBD-II
P241F: low-pressure EGR cooler efficiency below its threshold
P241F evaluates the measured cooling effect of the low-pressure EGR cooler against the available temperature difference.
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Documented application
2025 GM 25OBDG04B diagnostic parameter file; the cited monitor is documented, but individual vehicle, engine and calibration applicability has not been established.
The code alone does not identify a failed part or establish that a vehicle is safe to drive. Confirm the vehicle, reporting module and applicable service procedure.
P241F is a cooling-performance monitor for the low-pressure EGR cooler. The generic name calls it cooler B; the GM heading uses EGR 2 cooling system performance. Its efficiency calculation compares the exhaust-temperature drop across the cooler with the difference between inlet exhaust and inlet coolant temperatures.
A normalized cooling result
Samples receive a correction dependent on EGR flow before averaging. The documented failure threshold is efficiency below 40%, after 200 samples have been collected on a 100 ms task. Reporting is Type B, two trips. This is not a simple maximum outlet-temperature test.
The inlet exhaust-to-coolant temperature difference must be between 120°C and 300°C. Valid EGR flow, sufficient estimated coolant flow, operating-speed limits and valid temperature sensors are additional prerequisites. Those conditions ensure the calculation has a meaningful thermal reference.
What to compare next
Review inlet exhaust, outlet exhaust and inlet coolant information together. An outlet temperature alone cannot reproduce the ratio. Likewise, an invalid flow estimate can prevent a credible efficiency assessment even if the temperature signals appear reasonable.
Verification needs a completed average under qualified flow and temperature conditions. The code supports a cooling-efficiency concern, but the summary does not identify a particular blockage, coolant leak or failed valve. Component diagnosis should follow the exact vehicle procedure, including appropriate precautions around hot cooling and exhaust systems.
Source and application limits
This explanation covers the cited 2025 GM monitor. Confirm the vehicle and calibration in its service information before applying these limits; inclusion in this file does not establish model compatibility. GM diagnostic parameters, PDF page 1469. GM diagnostic parameters, PDF page 1470. GM diagnostic parameters, PDF page 1471.
Article source documents
Source checks describe how the text was prepared; they do not certify a diagnosis or confirm compatibility with every vehicle using this code.
Original code reference
Dictionary definition
EGR Cooler B Efficiency Below Threshold
This definition retains its original catalog scope. The article above is limited to its explicitly documented application.
Reference scope
Generic OBD-II definition.
A manufacturer label does not establish the model, year, engine or module to which a diagnosis applies. Read the safety and diagnostic limits.
Definition source
- DTC Database: pinned community code definitions
Source checked · MIT