P0175 on the 2020 Nissan Maxima: Diagnosis Guide
The 2020 Nissan Maxima is powered by the VQ35DE 3.5L V6 producing 300 hp, paired with the Xtronic CVT. This engine has been continuously refined and uses multi-port fuel injection. Bank 2 on the VQ35DE is the front cylinder bank (cylinders 1, 3, 5), positioned closest to the radiator. A P0175 code indicates the ECM has detected persistent over-fueling on this bank.
Common Symptoms
- Check engine light on
- Reduced fuel economy below the rated 20-30 MPG
- Rough or unsteady idle
- Black exhaust residue on bumper or tailpipe
- Hesitation during aggressive acceleration
- Fuel smell from exhaust
- Possible spark plug fouling
Causes Ranked by Likelihood
1. MAF Sensor Contamination (High Likelihood)
The Maxima's VQ35DE draws significant airflow through the MAF sensor at all operating conditions. At the mileage most 2020 models have reached (40,000-70,000 miles), years of PCV oil vapor and environmental contaminants coat the hot-wire element. The sensor underreports airflow, causing the ECM to calculate a richer mixture than needed. The MAF sensor is easily accessible in the intake tube and cleaning takes about 10 minutes with the right spray.
2. Bank 2 Upstream O2 Sensor Degradation (Medium Likelihood)
The upstream O2 sensor on the Maxima's Bank 2 sits in the front exhaust manifold. The Maxima's performance-oriented tuning means higher exhaust gas temperatures during spirited driving, which accelerates sensor wear. A degraded sensor with slow response time causes the ECM to overcompensate with fuel. At 40,000-70,000 miles, sensor degradation is becoming possible. Graph sensor voltage on a scan tool to assess response time.
3. Leaking Fuel Injectors (Medium Likelihood)
The VQ35DE's port fuel injectors deliver fuel to the intake ports. Over time, injector seals can deteriorate and the pintle valve can wear, allowing fuel to drip when the injector should be closed. On the Maxima's tuned-for-performance V6, the injectors work harder than on economy vehicles, accelerating wear. Perform a fuel pressure decay test to check for leaking injectors.
4. Fuel Pressure Regulator Issue (Low Likelihood)
The fuel pressure regulator maintains consistent fuel rail pressure on the returnless fuel system. If the regulator allows excessive pressure, every injector pulse delivers more fuel than commanded. This is the least common cause but is diagnosable with a fuel pressure gauge showing readings above the specified ~51 PSI at idle.
CVT Interaction on the Maxima
The Maxima's CVT is tuned for sporty driving with programmed shift points that simulate gear changes. When P0175 is active, the engine produces less power than the TCM expects, causing the CVT to adjust its ratio management. The simulated downshifts may feel more aggressive as the CVT tries to compensate for reduced power. Some owners report a slight drone or higher-RPM cruising when the code is present.
Diagnostic Steps
- Scan all codes. Check if P0172 is also present for system-wide vs. bank-specific diagnosis.
- Review freeze frame data for operating conditions at code set.
- Monitor Bank 2 STFT and LTFT. Negative LTFT beyond -10% confirms chronic enrichment.
- Clean the MAF sensor with dedicated MAF cleaner.
- Graph Bank 2 O2 sensor response time and voltage.
- Perform fuel pressure and injector balance testing if needed.
Repair Costs
MAF cleaning: $10-$15. MAF replacement: $120-$270. O2 sensor: $160-$330. Fuel injector: $130-$280 per injector. Fuel pressure regulator: $220-$450. Shop diagnostic time: $90-$150/hour.