Diagnostic article Generic OBD-II
P0480: Fan 1 relay-control opening detected with the driver off
P0480 explained through the documented GM monitor: fan 1 relay-control opening detected with the driver off. Diagnostic distinctions, verification and applicability limits.
Read before applying this article
Documented application
2025 GM 25OBDG03A ECM monitor at the cited physical PDF pages only. Vehicle, engine and calibration applicability is not established by the file-level application matrix.
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.
The cited GM P0480 monitor checks the cooling fan 1 relay-control low-side circuit for an open condition. Its heading explicitly excludes EREV, PHEV and HEV use for this row. It should not be assumed to describe every electrified vehicle carrying the same generic code.
Relay feedback is separate from fan speed
The failure evidence is low voltage during the driver's off state, interpreted by this controller as an open circuit. The associated internal specification is impedance above 200 kΩ between signal and controller ground. It is not a direct measurement of fan rotation or a universal fan-motor resistance test.
The monitor requires powertrain-relay voltage above 11 volts and uses fifty failures out of sixty-three samples at 100-millisecond intervals. Its Type B reporting and sampled window explain why a fault may be stored even if the fan later operates.
Interpret a paired code in context
The source notes that P0691 may also set on certain controllers. Two electrical labels need the correct driver procedure before being treated as separate defects. Record supply conditions and command state along with code status.
Verification should demonstrate a passing relay-driver circuit test, then the applicable system operation check. Seeing the fan turn once does not establish that its relay off-state feedback is correct. Use the approved cooling-system procedure and keep clear of an electrically controlled fan during any inspection.
Source and applicability
This explanation is limited to the 2025 GM 25OBDG03A monitor on page 305. Its thresholds are calibration examples, not universal specifications. Confirm the vehicle, engine and controller procedure 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
Fan 1 Control Circuit
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