P22A9: NOx sensor 2 heater-sense short to power

P22A9 is the high-voltage category for NOx sensor 2 heater sensing. The cited row describes a power short on HTemp, the connection used for heater resistance measurement. It does not establish that the heater element has reached an excessive temperature.

Reading the report correctly

The sensor's electrical fault classification is accepted with its bus relay on, supply above 9.90 V and powertrain relay voltage above 11 V. Dewpoint must be reached, and CAN communication and data validity must remain healthy. The controller evaluates 80 failed samples out of 160 on a 25 ms task; the table assigns Type B, two-trip reporting.

For Continental generation 3.5 sensors, the entry records an additional internal 1.5-second debounce used to identify electrical faults. That qualification is useful when interpreting delayed fault identification after an intermittent event.

Confirmation after diagnosis

Keep the sense-circuit identity separate from the heater-control high-voltage diagnosis P22A5. Both may involve the same sensor assembly, but the monitored paths differ. The next useful evidence is the exact circuit fault status under eligible operating conditions, supported by the vehicle-specific wiring procedure. A heater command or a single NOx ppm reading does not test HTemp integrity by itself. No pin location, probe method or universal replacement instruction is supplied by this summary table.

Source and application limits

This explanation covers the cited 2025 GM monitor. Confirm the vehicle and calibration in its service information before applying these limits; inclusion in this file does not establish model compatibility. GM diagnostic parameters, PDF page 1436.