Diagnostic article Generic OBD-II
P244B: filter pressure comparison suggests a downstream sensing problem
P244B uses hardware-dependent pressure comparisons to detect a leaking or disconnected downstream sensing pipe.
Read before applying this article
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.
The cited P244B strategy is aimed at a downstream pressure-sensing pipe that leaks or becomes disconnected. It should not automatically be read as proof that the particulate filter itself is blocked. The table documents two different implementations depending on sensor capability.
Two ways to test the downstream path
One implementation measures pressure downstream of the filter relative to ambient. The other evaluates differential pressure divided by exhaust mass flow over a calibrated window, against a map influenced by soot estimate and upstream temperature. The installed hardware determines which comparison is relevant.
Valid exhaust-flow information, qualified pipe-temperature conditions and absence of competing sensor faults are required. The continuation adds exhaust-valve, backpressure and temperature conditions. Reporting is Type A, one trip.
Important source limitation
The downstream-relative-pressure continuation prints a less-than threshold despite the “too high” heading, and some enable ranges are inconsistently presented. This article therefore avoids converting those cells into universal numerical test limits.
First identify which pressure architecture the vehicle uses, then evaluate its appropriate comparison and sensing paths. A differential-pressure measurement cannot substitute for the separate downstream-to-ambient measurement without knowing the architecture. Verification must confirm completion of the relevant monitor; neither the code name nor one high pressure reading establishes the required repair.
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 824. GM diagnostic parameters, PDF page 825. GM diagnostic parameters, PDF page 826. GM diagnostic parameters, PDF page 827. GM diagnostic parameters, PDF page 828.
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
Particulate Filter Differential Pressure Too High Bank 1
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