P0481: Fan relay channel two reports an electrical command mismatch

P0481 identifies the second cooling-fan relay control circuit in this GM ECM table. The monitor compares the requested output-driver state with the electrical state the controller observes. It does not directly measure cooling capacity or declare that a fan motor has failed.

A running fan is incomplete evidence

The test operates with fan operation and uses 20 failing samples out of 25, sampled every 250ms. Its enabling supply range is specified separately. Because the judgment concerns driver feedback, seeing a fan turn is not a complete substitute for knowing which relay channel was requested and whether its feedback matched.

The same page gives P0480 to relay channel one. Keep the channel identity in the diagnostic record: a result from the first output does not validate the second output. The document does not map “relay two” to a physical relay position or a particular fan-speed arrangement.

Make the next check specific

Save the requested fan state, the affected control channel, available output feedback and supply conditions at the time of failure. An event that appears only when a particular command changes should be evaluated with that transition preserved.

The table supports an electrical control-path investigation, but not a universal relay replacement. The matching wiring diagram and output-test instructions are needed to identify the real circuit. Cooling fans can start under controller command; keep hands and test leads clear, and use the prescribed service method rather than manually bridging relay terminals.

Source and applicability

GM 2010 10OBDG10 Hybrid Diagnostics, only the cited controller and monitor. These are historical calibration examples; individual vehicle, engine and hardware applicability is not established. GM PDF, page 79.