Diagnostic article Generic OBD-II
P27BF: Shift valve two circuit-low concerns driver feedback during switching
P27BF describes a short-to-ground classification for synchronizer valve two, separate from its hydraulic performance monitor.
Read before applying this article
Documented application
2025 GM 25OBDG07A Part 2 documented monitor only; its application-matrix filename join is unresolved. No model, engine or universal calibration 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.
P27BF maps to the electrical low check for synchronizer actuation valve two in this GM transmission. The driver reports a short-to-ground state after evaluating its monitored output node. The fault therefore concerns electrical behavior, not direct proof that the valve is hydraulically stuck off.
Why command state belongs in the record
The source describes the check during solenoid actuation and includes switching-timing qualifications. A static voltage sampled without its output command cannot reproduce that full evaluation. The listed DTC confirmation period is at least 150 ms.
The system must be outside safe state, with battery voltage above 8.75 V and below 18 V. Cranking and stop-key states are excluded; P0882 and P0883 disable the routine. A controller supply problem can therefore change which checks are eligible.
Separate the two diagnostic questions
First establish the driver’s reported electrical failure and the circumstances in which it returned. Hydraulic response and rod movement are assessed by other monitors and require their own evidence. Applicable service information must define the physical valve-two circuit and allowed measurement method. The source supplies no universal pinout and does not prove that replacing the valve coil, wiring or controller will repair the fault.
Document scope and source
2025 GM 25OBDG07A Part 2 documented monitor only; its application-matrix filename join is unresolved. No model, engine or universal calibration applicability is inferred. These figures explain the cited controller logic, not a vehicle-specific repair instruction. Match the vehicle’s service information before applying them.
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
Pressure Control Solenoid N Control Circuit Low
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