P0544: An exhaust-temperature circuit code can be a model-rationality result

P0544 is listed in Ford’s gasoline exhaust-temperature monitor as the bank 1 sensor 1 circuit/rationality entry, paired with P0544_92. Separate low and high electrical faults use different representations. The word “circuit” alone therefore does not establish that the sensor is electrically open.

The cold and running checks ask different questions

The offset check follows a six-hour engine-off soak and examines an early startup window. A reading above 250°C for two seconds in that cold-start context is different evidence from a hot operating sensor reaching the same temperature.

The running rationality check compares measured EGT with an inferred temperature, with a discrepancy exceeding 200°C for more than five seconds. It requires a defined operating window, inactive filter regeneration and closed-loop stoichiometric fueling. The summary lists a longer overall registration duration for inferred-model rationality than for the other checks.

Preserve the actual monitor opportunity

Record soak duration, startup timing, regeneration state and whether the comparison was against another inferred quantity rather than an electrical rail. Applying the cold-offset criterion to a fully warmed exhaust would misinterpret the source.

The document does not identify the cause of a model disagreement or authorize replacing the sensor from P0544 alone. Verification needs the applicable sensor architecture and eligible conditions, with electrical low/high findings kept separate from temperature plausibility evidence.

Source and applicability

Ford 2024–2025 gasoline OBD summary, July 16, 2024 revision; only the described monitor and architecture. Model, engine and calibration fitment are not inferred. The monitor explanation does not identify a failed part or replace the applicable service procedure. Ford PDF, page 6. Ford PDF, page 7.