P0175 on the 2020 Nissan Pathfinder: Bank 2 Running Rich
The 2020 Nissan Pathfinder uses the VQ35DD 3.5L V6 engine producing 284 hp, paired with a CVT transmission. This engine features direct fuel injection, variable valve timing, and variable valve lift. Bank 2 on the VQ35DD is the front cylinder bank (cylinders 1, 3, 5), closest to the radiator. A P0175 code means the ECM has detected that this bank is running richer than the target air-fuel ratio.
Symptoms You May Experience
- Check engine light illuminated
- Decreased fuel economy (below the rated 20-27 MPG)
- Rough or uneven idle
- Black exhaust smoke, especially during acceleration
- Reduced power during towing or climbing hills
- Fuel odor from the exhaust or engine compartment
Top Causes for the VQ35DD Engine
1. Contaminated MAF Sensor (High Likelihood)
The Pathfinder's V6 draws a large volume of air through the MAF sensor. Any contamination on the hot-wire element disproportionately affects fuel calculations because of the high airflow volume. Oil vapor from the PCV system is the primary contamination source. The MAF sensor is located in the intake tube between the air filter box and the throttle body. Clean it with MAF-specific cleaner as your first troubleshooting step.
2. Failing Bank 2 Upstream O2 Sensor (Medium Likelihood)
The upstream oxygen sensor on Bank 2 is mounted in the front exhaust manifold. On the Pathfinder, this sensor is exposed to significant heat, especially during towing. Heat cycling causes the sensing element to degrade over time. A lazy sensor with slow response leads the ECM to overcompensate with fuel. At the mileage range typical for 2020 models (40,000-70,000 miles), O2 sensor degradation is becoming more common.
3. Leaking Direct Fuel Injectors (Medium Likelihood)
The VQ35DD's direct injection system operates at very high fuel pressures (up to 2,900 PSI). The injectors on Bank 2 (cylinders 1, 3, 5) can develop carbon deposits around their tips that prevent proper sealing. A leaking injector delivers fuel even when the ECM commands it closed, enriching that bank. Nissan has issued technical service bulletins regarding injector carbon buildup on some VQ35DD applications.
4. Fuel Pressure Regulator Issue (Low Likelihood)
The high-pressure fuel pump and its internal regulator maintain precise fuel rail pressure. If the regulator sticks in a high-pressure position, every injector delivers more fuel per pulse than intended. This is less common but diagnosable with a fuel pressure gauge connected to the fuel rail test port. Compare readings against Nissan's specification of approximately 2,000 PSI at idle.
V6-Specific Considerations
When P0175 appears alone (without P0172 for Bank 1), the issue is isolated to the front bank. This narrows the diagnosis to Bank 2-specific components: the front O2 sensor, front bank injectors, or the front exhaust manifold gasket. If both P0172 and P0175 appear together, the cause is likely system-wide (MAF sensor, fuel pressure, or intake air leak).
Diagnostic Process
- Scan for all codes. Check if P0172 is also present.
- Review freeze frame data for engine RPM, load, and temperature when the code set.
- Monitor Bank 2 STFT and LTFT. Values more negative than -10% confirm the rich condition.
- Clean the MAF sensor and clear codes.
- Graph the Bank 2 upstream O2 sensor response time.
- Perform a relative compression or injector balance test on Bank 2 cylinders.
Estimated Repair Costs
MAF cleaning: $10-$15. MAF replacement: $130-$300. Bank 2 O2 sensor: $180-$370. Fuel injector replacement: $300-$550 per injector on the DI system. Fuel pressure regulator/pump: $450-$800. Diagnostic time: $100-$160/hour for V6 diagnosis.