Diagnostic article Generic OBD-II
P04D2: intermittent upstream low-pressure EGR temperature behavior
P04D2 evaluates intermittent or erratic behavior in the upstream low-pressure EGR temperature signal.
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Documented application
2025 GM 25OBDG04B diagnostic parameter tables; the cited monitor only. Vehicle, engine and calibration applicability must be confirmed separately.
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.
P04D2 evaluates intermittent or erratic behavior in the upstream low-pressure EGR temperature signal. Its strategy uses limits related to the last good reading and the sensor's filtering response.
The history of the signal matters
The table describes upper and lower thresholds that blend sensor limits with the last accepted temperature. The blend also depends on consecutive failed samples, sampling time and filter response time. This is more than a simple check that every reading remains between two fixed temperatures.
The threshold column lists 320°C and −60°C as boundary values, but the accompanying equations describe the dynamic evaluation. Treating those numbers as the entire pass/fail rule would omit how the monitor responds after a sudden change.
Separate erratic behavior from an electrical-range fault
No EGR temperature electrical fault may already be detected. The engine must not be cranking, relay voltage must exceed 11 V and the test must be enabled. The failure filter is 60 counts among 75 samples on a 100 ms task, with Type A reporting.
A useful review preserves the last valid value and the sequence of changes, not only a final steady reading. Verification should demonstrate consistent valid feedback during an eligible assessment. The source does not prove an intermittent harness fault or defective probe by itself, and its extracted filter expression should not be used to recreate calibration logic without the exact service definition.
Source and applicability
2025 GM 25OBDG04B diagnostic parameter tables; the cited monitor only. Vehicle, engine and calibration applicability must be confirmed separately. These tables describe detection logic, not a complete repair procedure or a component replacement verdict. gm-2025-04b, PDF page 1213.
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 Temperature Sensor C Circuit Intermittent/Erratic
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