Diagnostic article Generic OBD-II
P2CBA: Fan 2 speed above the controller’s estimated allowance
P2CBA compares fan 2 speed with an estimated reference and a calibration table, rather than using one universal fan-speed limit.
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Documented application
2025 GM 07A-2 documented monitor only; module and calibration applicability must be matched to the vehicle. The application-matrix filename join remains unresolved; no model or engine fitment 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.
P2CBA is the fan 2 overspeed monitor in the cited GM controller. Its failure expression is actual fan speed minus the maximum estimated fan speed, compared with a calibration-dependent limit. The quantity being judged is therefore a speed difference, not just the fan's displayed revolutions per minute.
Why the lookup table matters
The summary gives a threshold range of 1,400 to 4,050 rpm and refers to lookup table 36. It lists a twenty-second qualification and a two-trip response. The complete threshold selection is not provided in the row, so neither end of that range should be promoted to a universal pass/fail speed.
The monitor also references commanded fan percentage, battery and general enable conditions. Command information matters because the estimated allowance is part of the comparison. A high actual speed can be expected under one demand state and excessive relative to the reference under another.
Retain actual and expected speed
Where diagnostic data permits, preserve actual fan 2 speed, the estimated reference, command and monitor status together. A single tachometer value without the reference cannot reconstruct the published decision. The adjacent fan 2 underspeed row evaluates a different condition and should not be substituted for this check.
The table does not prove a failed fan module or identify a control-wire fault. Confirmation requires the correct calibrated comparison during an enabled interval. Cooling fans can operate unexpectedly, so access and physical testing must follow the vehicle procedure; no hand contact or improvised restraint of a running fan is appropriate.
Source and applicability
2025 GM 07A-2 documented monitor only; module and calibration applicability must be matched to the vehicle. The application-matrix filename join remains unresolved; no model or engine fitment is inferred. GM PDF, page 816.
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
Fan 2 Overspeed
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