P0174 System Too Lean (Bank 2)
The Bank 2 equivalent of P0171: fuel trim on Bank 2 is maxed out trying to compensate for a lean condition.
Definition
P0174 is the Bank 2 counterpart to P0171. When P0171 and P0174 appear together, the cause is almost always a shared component (MAF, intake gasket, large vacuum leak) rather than a bank-specific part.
Common causes
- Shared vacuum leak affecting both banks
- Failing MAF sensor
- Weak fuel pump
Common misdiagnoses
- Chasing bank-specific causes when both P0171 and P0174 are present together.
Troubleshooting steps
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1. Confirm whether P0171 is also present
If both codes set together, focus on shared causes (MAF, large vacuum leak, fuel pump).
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2. Follow the P0171 procedure
Apply the lean-condition diagnostic steps to the shared components first.