P2204 indicates an intermittent signal from the NOx (nitrogen oxide) sensor on Bank 1, Sensor 1 (upstream of the catalyst). The ECM detects irregular voltage or resistance readings that vary while the engine is running.
The sensor element or its internal circuitry can fail intermittently, causing erratic voltage signals.
Corroded, loose, or damaged wires or connectors between the sensor and the ECM can create intermittent communication.
A leak upstream of the sensor can introduce extra oxygen, confusing the sensor and producing unstable readings.
Incorrect coolant temperature data can affect NOx sensor operation, leading to intermittent signals.
Rarely, the ECM may have a failing input circuit for the NOx sensor, but this is usually a last‑resort diagnosis.
No. Replacing the PCM is almost never necessary for this code. The problem is almost always a sensor, wiring, or exhaust issue.
Yes. An intermittent NOx sensor can cause the engine to run rich or lean, leading to rough idle, hesitation, and reduced fuel economy.
Driving is possible, but the vehicle may run less efficiently and could fail an emissions test. Repair is recommended to avoid possible catalytic converter damage.
NOx sensors typically last 100,000–150,000 miles, but premature failure can occur due to contamination, heat exposure, or exhaust leaks.