P2206: NOx heater-control short to ground after dewpoint

P2206 is the low-circuit diagnosis for the engine-out NOx sensor's heater-control connection. In the reviewed GM table, its specific fault mechanism is a short to ground on the heater-control pin. It does not mean that the NOx concentration itself is low.

Dewpoint is an enable condition

The source requires the sensor's dewpoint condition to be reached before this short-to-ground monitor is eligible. That differs from the adjacent heater-control open-circuit row, which does not list the same gate. A quick key-on check may therefore not exercise P2206 even when communication and supply appear normal.

Other prerequisites are powertrain-relay voltage above 11 volts, sensor supply above 9.90 volts and a commanded-on NOx bus relay. Lost communication and invalid CAN-frame faults must be absent.

Qualification and interpretation

The counter needs 80 failures within 160 samples at 25 milliseconds per task, with Type B reporting over two trips. These sample counts describe qualification of the electrical status; they do not identify where the ground path lies or prove a failed sensor assembly.

Verification should confirm that the dewpoint and electrical prerequisites permit the heater-control check, then examine its result. A normal heater-temperature reading on another diagnostic channel cannot independently prove this control connection is healthy. The source supplies no pin-voltage limit or circuit isolation procedure. Apply the monitor facts only after confirming the installed sensor system and vehicle-specific service information; the generic code alone does not establish model coverage.

Source: GM monitor, PDF page 1411.