Diagnostic article Generic OBD-II
P02CB: bank-2 underboost monitoring and a calibration caveat
P02CB is labeled a bank-2 underboost condition in the cited table.
Read before applying this article
Documented application
2025 GM 25OBDG07A Part2 diagnostic monitor documentation; the application-matrix filename mismatch is unresolved, so no model or engine applicability is inferred.
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.
P02CB is labeled a bank-2 underboost condition in the cited table. It compares an averaged boost-control deviation within a qualified operating window, rather than treating every low pressure reading as an underboost fault.
Confirm demand and measurement validity
The row requires valid desired values, a valid bank-2 sensed value, active boost control, and no relevant safety-cutoff or limp-home request. It also lists desired pressure upstream of the bank-2 throttle above 1,600 hPa and ambient pressure above 700 hPa.
These conditions distinguish insufficient pressure during a valid boost demand from low pressure when no such demand exists. A diagnostic review should retain desired pressure, sensed pressure, and their validity status together.
Do not turn the printed formula into a repair limit
The source’s comparison references a 250-hPa value and a 50-hPa difference described as healing a minimum error. It also prints both a wide-open-throttle-area condition and an idling-active condition. Those details are not clear enough to reconstruct a dependable universal failure threshold.
Two-trip reporting and a three-second operating qualifier are shown. Verification should use the applicable service calibration’s completed underboost test. This draft remains flagged for source review because the failure-versus-healing formula and operating-state wording need resolution before numerical diagnostic instructions can be published.
Documentation and applicability
These details describe the monitor in GM’s 2025 25OBDG07A Part2 file. Its application-matrix filename does not match the download index, so model and engine applicability remain unresolved. Use the vehicle’s correct service information before applying these calibration details.
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
Turbocharger/Supercharger B Underboost Condition
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