Diagnostic article Generic OBD-II
P27F0: Mode-valve feedback fails to follow a range command
Understand why P27F0 uses range transitions, hydraulic availability and independent transmission states rather than one sensor-voltage limit.
Read before applying this article
Documented application
2025 GM 25OBDG03B documented monitor only. Vehicle, engine and calibration applicability must be confirmed from the matching service information; no model 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.
P27F0 evaluates whether mode-valve B position changes appropriately when electronic range selection commands a new state. Its GM logic is substantially different from the neighboring raw-voltage faults: an electrically plausible signal can still fail to represent the required transition or final position.
Commanded state determines the expected evidence
The monitor considers Park, Reverse, Drive and several neutral states. Depending on the transition, it combines position feedback with hydraulic-pressure availability, mode-valve commands, park-servo state and sometimes slip determination. A disagreement in one operating branch cannot be interpreted using another branch’s timing or expected position.
The source uses transition-specific delay limits and additional steady-state checks. It does not provide one universal number of seconds that can be applied to every range change. The actual commanded direction and diagnostic range must remain attached to the fault record.
Establish signal validity before judging performance
Related mode-valve electrical faults, including P27EF, P27F1 and P27F2, are among the exclusions in the relevant branches. Hydraulic and high-side-driver conditions also matter. If those prerequisites are absent, the performance inference should not be treated as a direct observation of a stuck mechanism.
Preserve the command sequence, feedback transition and independent hydraulic or park-state evidence. P27F0 can guide an investigation of inconsistent range-control behavior, but the summary alone does not select a position sensor, solenoid or internal valve for replacement.
Source and applicability
2025 GM 25OBDG03B documented monitor only. Vehicle, engine and calibration applicability must be confirmed from the matching service information; no model fitment is inferred. These criteria explain controller logic, not a complete repair procedure. 25OBDG03B, PDF page 1698. 25OBDG03B, PDF page 1699. 25OBDG03B, PDF page 1700. 25OBDG03B, PDF page 1701. 25OBDG03B, PDF page 1702.
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
Transmission Range Control B Position Sensor/Switch Circuit Range/Performance
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