What Does P0172 Mean on Your 2020 Nissan Maxima?
A P0172 code on the 2020 Nissan Maxima means the engine control module has detected that Bank 1 is running too rich. The 2020 Maxima is powered by the 3.5L VQ35DE V6 engine producing 300 horsepower and 261 lb-ft of torque. This engine uses port fuel injection. Bank 1 on the transverse-mounted V6 is the rear bank closest to the firewall.
As Nissan's flagship sedan, the Maxima deserves proper attention when a fuel system issue arises. A rich condition wastes fuel, can foul spark plugs, and puts stress on the catalytic converter. Getting this fixed promptly protects your investment.
Common Symptoms You May Notice
- Check engine light on
- Reduced fuel economy
- Rough or surging idle
- Black exhaust smoke
- Fuel smell at the tailpipe
- Reduced power and throttle response
Top Causes of P0172 on the 2020 Maxima
- Dirty MAF sensor - The mass airflow sensor accumulates contamination over time. This is the most common cause of P0172 on the Maxima and the easiest to fix.
- Aging upstream O2 sensor - The Bank 1 upstream oxygen sensor can degrade with mileage, sending incorrect voltage readings for fuel trim calculations.
- Leaking fuel injector - Port fuel injectors can develop leaks or deposits after years of service, causing uneven fuel delivery on Bank 1.
- EVAP purge valve malfunction - A stuck-open purge valve allows fuel vapors to continuously enter the intake manifold.
How to Diagnose the Problem
Scan for codes and review freeze frame data. Check Bank 1 STFT and LTFT values. Negative LTFT past -10% confirms the rich condition.
Replace the air filter if it has not been changed recently. Clean the MAF sensor with proper MAF cleaner spray. The Maxima's MAF is in the air intake tube, accessible after removing the air filter box lid.
Monitor the Bank 1 upstream O2 sensor with live data. It should oscillate between 0.1V and 0.9V quickly. A slow or stuck sensor needs replacement.
If only Bank 1 is rich, focus on rear bank components. If both banks show rich, suspect the MAF sensor or fuel pressure.
Repair Options and Cost Estimates
- MAF sensor cleaning or replacement: Cleaning under $10. New sensor $40-$140 plus $35-$85 labor.
- O2 sensor replacement: Parts $40-$140. Labor $65-$135.
- Fuel injector replacement: Parts $25-$70 per injector. Labor $140-$310.
- EVAP purge valve: Parts $20-$50. Labor $40-$90.
Can You Fix This Yourself?
MAF cleaning is easy on the Maxima. O2 sensor replacement is moderate but accessible. Port injector replacement is doable for intermediate DIYers since port injectors are simpler than direct injection. The Maxima's engine bay is somewhat tight due to the transverse V6 layout.
Prevention Tips
- Replace the air filter every 15,000-20,000 miles
- Use premium fuel as recommended by Nissan for the Maxima
- Run fuel system cleaner every 5,000 miles
- Consider replacing O2 sensors proactively around 80,000-100,000 miles