A fixed extreme temperature on a scan tool needs interpretation alongside circuit codes and tool support. It may be a substituted or invalid value rather than the actual exhaust temperature.
Keep the unedited parameter
Record its name, units, sensor position and whether the engine was cold or running. Include recent exhaust or wiring work. Do not compare unnamed temperature channels as if they measured the same location.
The technician should follow the relevant circuit and plausibility checks. Avoid regeneration or other high-temperature procedures until the fault is understood. A replacement recommendation should be supported by evidence distinguishing the sensor, connection and displayed interpretation, not merely the alarming size of a number.
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