What P0174 Means on Your 2021 Honda Pilot
A P0174 code on the 2021 Honda Pilot indicates the engine control module has detected a lean air-fuel mixture on Bank 2. The 2021 Pilot is powered by a 3.5-liter V6 engine producing 280 hp and 262 lb-ft of torque, paired with either a 6-speed or 9-speed automatic transmission. Since this is a V6 engine with two cylinder banks, the P0174 code correctly identifies that Bank 2 (the bank closer to the firewall) is running lean.
A lean condition means the engine is receiving too much air or not enough fuel on that bank. This can cause rough running, poor performance, and elevated combustion temperatures that risk engine damage over time.
Symptoms
- Check engine light on
- Rough or uneven idle
- Hesitation or stumbling during acceleration
- Reduced power, especially from Bank 2 cylinders
- Engine running warmer than normal
- Possible misfires on Bank 2
Common Causes on the 3.5L V6
- Vacuum Leak on Bank 2 - Cracked vacuum lines, a leaking intake manifold gasket on the rear bank, or PCV system issues can allow unmetered air into Bank 2 cylinders. The rear bank is harder to inspect visually.
- Dirty MAF Sensor - A contaminated mass airflow sensor underestimates total airflow, leading to insufficient fuel delivery across both banks. If only Bank 2 shows lean, a vacuum leak is more likely.
- Clogged Fuel Injector on Bank 2 - A partially clogged injector on one of the Bank 2 cylinders restricts fuel flow to that cylinder, creating a localized lean condition.
- Faulty Bank 2 O2 Sensor - The upstream oxygen sensor on Bank 2 provides feedback for fuel trim adjustments on that bank. A failing sensor causes incorrect corrections.
Diagnostic Steps
- Scan for all codes - Check if P0171 (Bank 1 lean) is also present. Both banks lean suggests a common cause like MAF sensor or fuel pressure. Only Bank 2 lean points to a bank-specific issue.
- Check for vacuum leaks near Bank 2 - Inspect vacuum hoses and the intake manifold gasket on the rear bank. A smoke test is highly recommended since the rear bank is difficult to access visually.
- Clean the MAF sensor - Remove and clean with dedicated spray.
- Monitor fuel trims by bank - Compare Bank 1 and Bank 2 STFT and LTFT values. If only Bank 2 is showing high positive values, the issue is bank-specific.
- Test fuel injectors - Perform an injector balance test or use a scan tool to check injector pulse width and fuel trim by cylinder.
Repair Costs
The Honda Pilot is a midsize SUV with moderate repair costs.
- Vacuum hose replacement - $5 to $30 for parts, plus $80 to $150 labor due to rear bank accessibility.
- Intake manifold gasket - $40 to $90 for gaskets, plus $250 to $450 labor on the V6.
- MAF sensor cleaning - $10 to $25.
- MAF sensor replacement - $90 to $200, plus $50 to $100 labor.
- Fuel injector replacement - $60 to $140 per injector, plus $200 to $400 labor for rear bank access.
- O2 sensor replacement - $70 to $170 for the sensor, plus $80 to $160 labor.
DIY Feasibility
MAF sensor cleaning and replacement are straightforward DIY jobs. Vacuum leak checks on the front of the engine are manageable, but rear bank work on the V6 can be challenging due to limited access. O2 sensor replacement is doable with a sensor socket. Intake manifold gasket and fuel injector work on the rear bank typically require more experience and patience.
Prevention Tips
- Inspect vacuum hoses during routine service
- Use quality air filters and replace them on schedule
- Run a fuel system cleaner through the tank periodically
- Follow Honda's maintenance schedule for spark plugs and filters
- Address check engine lights promptly to prevent secondary damage