2009 Mercedes GL320 P2201 Code: NOx Sensor Fault Diagnosis and Repair Guide
I own a 2009 Mercedes-Benz GL320 with 76,000 miles. Over the past several weeks, I've been receiving a P2201 diagnostic trouble code, which indicates a fault in the NOx (nitrogen oxide) sensor. The vehicle has multiple NOx sensors, and I'm unsure how to determine exactly which one is failing based on this code. What's the recommended first step—should I inspect and clean the affected sensor(s), or is replacement necessary? Are there specific procedures for replacing NOx sensors in a 2009 GL320? Does the vehicle require re-adaptation after replacement? Any practical advice or troubleshooting steps would be greatly appreciated. Mike
I recently dealt with a similar issue on my 2009 GL320 (though I had P2202, not P2201), and I replaced both NOx sensors. The process involved soaking them in alcohol, spraying with brake cleaner, then using compressed air to blow out any debris before reinstallation. I let the sensors dry for at least 24 hours before driving. After just 40 miles, the P2202 code has not returned—though I'm still cautious. I've read that after replacing NOx sensors, the vehicle must undergo a re-adaptation process to recalibrate the system. What steps did you take to resolve your P2201 issue? Thanks for any insights!