P22A6: open NOx sensor 2 heater-sense circuit

P22A6 addresses the heater-sense circuit of NOx sensor 2. The source identifies the monitored connection as HTemp, used for heater resistance measurement, and diagnoses an open load at that pin. This is distinct from the heater-control open-circuit code P22A3.

Why the sense path matters

A heater may be commanded on while its feedback path remains electrically invalid. The code therefore should not be interpreted solely from whether the sensor becomes warm. The evidence required here is integrity of the heater-resistance measurement circuit.

The GM counter is 80 failures out of 160 samples on a 25 ms task. Powertrain relay voltage above 11 V, sensor supply above 9.90 V and a commanded-on bus relay qualify the check. Lost-communication and invalid-data conditions must be absent. The entry is Type A, one trip.

Timing and confirmation

The table additionally notes a 1.5-second internal electrical-fault debounce for Continental generation 3.5 NOx sensors. That sensor-specific processing helps explain why a circuit interruption and its final reported identity need not appear at the same instant; it should not be added blindly to every vehicle's timing.

Confirm the exact sensor architecture and service test before probing. Verification should show that the HTemp open-load report is resolved while communication and supply conditions are valid, not merely that a generic heater command can be issued.

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 1433.