What Does P0172 Mean on Your 2020 Nissan Pathfinder?
A P0172 code on the 2020 Nissan Pathfinder means the engine control module has detected that Bank 1 is running too rich. The 2020 Pathfinder is powered by the 3.5L VQ35DD V6 engine producing 284 horsepower and 259 lb-ft of torque with direct injection. Bank 1 on this V6 is the rear bank closest to the firewall.
A rich condition means excess fuel relative to air in the combustion process. This wastes fuel on a three-row SUV that already has significant fuel demands, and can damage the Bank 1 catalytic converter over time.
Common Symptoms You May Notice
- Check engine light on
- Decreased fuel economy
- Rough or uneven idle
- Black exhaust smoke
- Fuel smell at the tailpipe
- Hesitation or sluggish response
Top Causes of P0172 on the 2020 Pathfinder
- Dirty MAF sensor - The mass airflow sensor is the leading cause. Road dust contaminates the sensing element, causing underreported airflow and excess fueling.
- Faulty upstream O2 sensor - The Bank 1 upstream oxygen sensor can degrade over time, providing inaccurate readings for fuel trim adjustments.
- Leaking fuel injector - The 3.5L VQ35DD uses direct injection. A leaking Bank 1 injector delivers excess fuel.
- EVAP purge valve malfunction - A stuck-open purge valve sends fuel vapors into the intake continuously.
How to Diagnose the Problem
Scan codes and review freeze frame data. Check Bank 1 STFT and LTFT. Negative LTFT past -10% confirms the rich condition.
Clean the MAF sensor with dedicated MAF cleaner spray. The Pathfinder's MAF is in the air intake tube. Monitor the Bank 1 upstream O2 sensor; it should oscillate between 0.1V and 0.9V.
If only Bank 1 shows rich trims, focus on Bank 1 (rear) components. If both banks are affected, suspect the MAF sensor or fuel pressure.
Repair Options and Cost Estimates
- MAF sensor cleaning or replacement: Cleaning under $10. New sensor $45-$150 plus $40-$90 labor.
- O2 sensor replacement: Parts $45-$145. Labor $70-$140.
- Fuel injector replacement: Parts $35-$95 per injector. Labor $175-$380.
- EVAP purge valve: Parts $20-$50. Labor $45-$95.
Can You Fix This Yourself?
MAF cleaning is easy. O2 sensor replacement on the rear bank is moderate but accessible from under the vehicle. Fuel injector work on the direct injection V6 is advanced and typically requires professional help.
Prevention Tips
- Replace the air filter every 15,000-20,000 miles
- Use quality fuel to keep direct injectors clean
- Run fuel system cleaner every 5,000 miles
- Address check engine lights promptly