Nissan Micra K11 1.0L Petrol 2001 - P0171 and P0420 Fault Codes Explained
Hi, I own a 2001 Nissan Micra K11 1.0L petrol engine, and I'm currently experiencing two diagnostic trouble codes: P0171 (Rich Fuel Mix in Bank 1) and P042-20 (Catalyst System Efficiency Below Threshold). I recently tried unplugging the MAF sensor to test its influence on engine performance — unfortunately, the car ran significantly worse after that. Below is a data stream captured with the MAF sensor reconnected and the codes cleared. The engine was fully warmed up and operating in Closed Loop mode. However, when I briefly blipped the throttle, it momentarily entered Open-Loop Drive (OL-DRIVE). FUELSYS1 OL-DRIVE ETC °C: 80 SHRTFT1: -7.8 LONGFT1: 0.0 RPM: 640 SPARKADV: 14 IAT °C: 28 MAF g/s: 1.57 TP %: 8.6 O2B1S1 V: 0.760 O2B1S2 V: 0.735 Can anyone identify any unusual readings or potential root causes in this data stream? Thanks for your help!
Monitor O2B1S1 at idle to observe switching between 0.2V and 0.7V every second. If the sensor remains stuck at 0.7V, it may indicate a vacuum leak or faulty oxygen sensor. To test this, introduce a controlled vacuum leak — if the voltage does not drop to 0.2V, the O2 sensor is likely defective.