What P0174 Means on Your 2020 Nissan Maxima
Your 2020 Nissan Maxima has stored a P0174 trouble code, indicating Bank 2 of the engine is running lean. The 2020 Maxima is powered by a 3.5-liter V6 engine (VQ35DE) producing 300 horsepower, paired with a CVT transmission. As a V6, this engine has two cylinder banks -- Bank 2 is the rear bank near the firewall.
P0174 means the engine control module (ECM) has detected that its fuel trim corrections on Bank 2 have exceeded the normal threshold. The ECM has been adding fuel to correct a lean mixture, but the condition persists beyond its ability to compensate.
Symptoms You Might Notice
- Check engine light on
- Rough or inconsistent idle, especially at stoplights
- Noticeable loss of the Maxima's typical acceleration punch
- Decreased fuel economy from the normal 20/30 MPG range
- Hesitation or stumbling during spirited driving
- Possible engine misfires at low RPM
Common Causes for the 2020 Maxima
- Vacuum Leak on Bank 2 (35% likelihood) -- The VQ35DE has a complex intake system with multiple gaskets and hoses. Rear bank leaks are common and difficult to visually inspect.
- Contaminated MAF Sensor (25% likelihood) -- The mass airflow sensor can get fouled by oil vapor from the PCV system or a neglected air filter.
- Bank 2 Fuel Injector Issue (25% likelihood) -- Clogged or partially restricted injectors on the rear bank reduce fuel delivery to those three cylinders.
- Exhaust Leak Near Bank 2 O2 Sensor (15% likelihood) -- A crack in the exhaust manifold or loose gasket on the Bank 2 side introduces air that makes the O2 sensor read lean.
Diagnosis Steps
- Scan for all trouble codes -- Check for P0171 (Bank 1 lean), misfire codes, and O2 sensor codes to understand the full picture.
- Analyze fuel trim data -- Compare Bank 1 and Bank 2 short-term and long-term fuel trims. Bank 2 LTFT above +15% confirms the issue.
- Perform a smoke test -- Inject smoke into the intake to locate vacuum leaks on the rear bank of the VQ35DE.
- Test MAF sensor readings -- Compare live data to factory specifications at idle and under load.
- Check fuel pressure and Bank 2 injectors -- Verify fuel rail pressure and test individual injector flow rates.
Repair Options
- Repair vacuum leaks -- Replace cracked hoses, loose fittings, or leaking intake manifold gaskets on Bank 2.
- Service the MAF sensor -- Clean with MAF-specific cleaner or replace if readings remain out of spec.
- Clean or replace fuel injectors -- Professional ultrasonic cleaning or new injectors for the rear bank.
- Fix exhaust leaks -- Replace exhaust manifold gaskets or repair cracked pipes on the Bank 2 side.
Estimated Repair Costs
- Vacuum leak repair: $150 - $500
- MAF sensor replacement: $180 - $400
- Fuel injector service/replacement: $280 - $700
- Exhaust leak repair: $200 - $600
The Maxima is Nissan's premium sedan, so parts can be slightly more expensive than economy models, but labor rates are comparable.
Prevention Tips
- Replace the engine air filter every 15,000-20,000 miles
- Use premium fuel as recommended by Nissan for the Maxima's V6
- Have vacuum lines and connections inspected at every major service
- Address check engine lights promptly to prevent secondary damage
- Follow Nissan's maintenance schedule for the Maxima