P2205: NOx sensor 1 heater-control open-circuit diagnosis

P2205 is an open-circuit diagnosis for the engine-out NOx sensor's heater-control path. The reviewed GM row identifies the heater-control pin specifically. It does not describe an open in the separate heater-temperature sensing path or a direct NOx concentration problem.

Control and sensing are different circuits

The source's distinction is useful when several NOx heater codes are present. P2205 concerns the circuit that controls heating; the nearby heater-sense code concerns the measurement connection used to assess resistance. A broad description such as “NOx heater fault” loses that diagnostic direction.

The page gives an open-circuit status rather than a numeric resistance threshold. It therefore supports the fault category but not a universal meter test or an automatic decision to replace the sensor assembly.

Conditions for a valid result

The NOx bus relay must be commanded on, powertrain-relay voltage must exceed 11 volts and sensor supply exceed 9.90 volts. Lost communication and invalid sensor CAN data must be absent. Unlike some neighboring heater-short monitors, this row does not list dewpoint as an enable condition.

Qualification uses 80 failing samples within 160 on a 25-millisecond task. Reporting is Type A, one trip. Verification should establish a valid open-load diagnosis with supply and communication prerequisites satisfied; a missing result caused by communication loss is not a pass. Exact sensor hardware, terminal identification and safe circuit isolation require vehicle-specific service information. These facts describe only the documented 2025 GM monitor.

Source: GM monitor, PDF page 1410.