Summary
P0174 means the engine's air-fuel mixture on Bank 2 is too lean — too much air or not enough fuel. If P0171 (Bank 1 lean) is also present, the cause is in a system shared by both banks — typically a vacuum leak, dirty MAF sensor, or weak fuel pump. If only P0174, the cause is bank-specific: a vacuum leak on the Bank 2 side or a failing fuel injector. Start with the cheapest checks: vacuum hoses and MAF sensor cleaning ($8).
Severity: Moderate
Safe to drive: Yes, short distances — lean running damages catalytic converters over time
Repair cost: $8–$600 depending on cause
DIY difficulty: Easy to Moderate
What does P0174 mean?
P0174 is identical in meaning to P0171, but for Bank 2 (the side without cylinder 1 on V-configuration engines). The PCM has been adding extra fuel to Bank 2 to compensate for a lean condition, and has exceeded its correction limit (typically +20–25% long-term fuel trim).
The key diagnostic question: Is P0171 also present?
- Both P0171 and P0174: The cause is in a shared system — MAF sensor, fuel pump, fuel pressure regulator, or a large central vacuum leak.
- Only P0174: The cause is specific to Bank 2 — a vacuum leak on that side, a Bank 2 injector issue, or an exhaust leak before the Bank 2 upstream O2 sensor.