Diagnostic article Generic OBD-II
P27CF: Valve-four circuit low is an electrical report, not a hydraulic verdict
P27CF identifies the synchronizer valve-four driver’s ground-side classification and depends on valid controller operating conditions.
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.
P27CF refers to the electrical low diagnostic for synchronizer actuation valve four in this GM file. The driver’s monitored-node evaluation reports a short-to-ground state. That report is different from a hydraulic performance monitor declaring that the valve remained off.
Keep switching context with the signal
The source describes the test while the solenoid is actuated and supplies internal switching-time qualifications. Interpreting one voltage value without command timing can therefore misrepresent what the controller tested. The DTC confirmation interval is at least 150 ms.
The controller must not be in safe state. Battery voltage must exceed 8.75 V and remain below 18 V; cranking and stop-key conditions are excluded. P0882 or P0883 inhibits this check, which makes a broader supply failure relevant to the test’s eligibility.
Verification and component isolation
Retain valve-four command, driver fault status and supply evidence together. A rod-motion test may answer a hydraulic question but cannot replace this electrical evidence. Confirm the specific circuit through the vehicle’s service information before assigning the generic solenoid-R label to hardware. The summary does not determine whether the cause lies in the valve coil, external circuit or output stage.
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 R 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