Diagnostic article Generic OBD-II
P283C: Rod-three consistency is tied to the even-clutch speed references
P283C uses learned rod-three positions and independently supported even-side gear evidence to judge whether position feedback is believable.
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.
P283C identifies rod-three position inconsistency in the cited transmission. Its dynamic engagement branch compares the sensor with a learned engaged position while speed signals indicate the gear has engaged. A disagreement greater than 1,100 micrometres is evaluated only with adequate force request and without an electrical sensor fault.
Validate the reference before condemning the sensor
The static branch checks learned tolerance bands with no outside rod force. It then verifies even-clutch speed against engine speed and output speed against driven-wheel information. The source lists a 500 ms out-of-limits interval, making the independent-reference check part of confirmation rather than an optional observation.
A second path checks for frozen feedback
The integrity routine attempts small rod-three moves in both directions. If motion remains no greater than 100 micrometres, a complementary rod-four movement through a shared valve must demonstrate that the actuation path can work. That comparison helps separate stuck position feedback from a valve failure.
Preserve the actual branch, learned locations, force commands and confirming speed or alternate-rod evidence. A single plausible rod position cannot verify every route. The generic fork-C label is not a universal component location; intrusive tests and final isolation require the relevant transmission service procedure.
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.
GM physical PDF page 966, GM physical PDF page 967, GM physical PDF page 968.
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
Shift Fork C Position 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