What Does P0174 Mean?
The engine is running too lean on bank 2. The ECM has detected that long-term fuel trim on bank 2 has exceeded the positive correction limit, meaning the system is adding significantly more fuel than normal to compensate for excess unmetered air or insufficient fuel. This is the bank 2 equivalent of P0171. The driver may notice rough idle, hesitation, misfires, and poor fuel economy.
Common Causes
35%
Vacuum leak on the bank 2 side — cracked hose, loose intake manifold gasket, or leaking PCV system
25%
Dirty or failing MAF sensor under-reporting airflow to the ECM
20%
Low fuel pressure from a weak fuel pump, clogged filter, or faulty pressure regulator
12%
Clogged or restricted fuel injectors on bank 2 delivering insufficient fuel
8%
Exhaust leak upstream of the bank 2 sensor 1 O2 sensor
Diagnostic Steps
1
Compare STFT and LTFT between bank 1 and bank 2. If only bank 2 is lean, the cause is bank-specific (vacuum leak, injector issue, or exhaust leak on bank 2). If both banks are lean, suspect MAF or fuel delivery.
2
Perform an intake smoke test with emphasis on the bank 2 side. Check intake manifold gasket, intake runner seals, brake booster line (if bank 2 side), and all vacuum tees and hoses.
3
Clean the MAF sensor and verify its output matches known-good specs. On many vehicles, the MAF should read 2–7 g/s at idle and scale linearly with RPM.
4
Measure fuel pressure at the rail. Spec is typically 35–65 psi depending on the fuel system type. Pressure should remain stable at idle and not drop under snap acceleration.
5
If the lean condition is isolated to bank 2, perform an injector flow balance test or use an injector pulse width comparison to identify restricted injectors on that bank.
Estimated Repair Cost
$75 - $800
Parts + labor, varies by vehicle and location
The engine is running too lean on bank 2. The ECM has detected that long-term fuel trim on bank 2 has exceeded the positive correction limit, meaning the system is adding significantly more fuel than normal to compensate for excess unmetered air or insufficient fuel. This is the bank 2 equivalent of...
The most common cause of P0174 (System too Lean (Bank 2)P0175 System too Rich (Bank 2)) is: Vacuum leak on the bank 2 side — cracked hose, loose intake manifold gasket, or leaking PCV system
Typical repair costs for P0174 range from $75 to $800, depending on the vehicle, location, and whether you do it yourself or go to a shop.
Drive with caution. A lean condition can cause misfires, detonation, and catalytic converter damage. Avoid heavy acceleration and towing until the issue is resolved. Severe lean conditions at high RPM can cause piston or valve damage.
Start by connecting an OBD2 scanner to read the code and any freeze frame data. Then follow the diagnostic steps specific to P0174 to identify the root cause.
OBDHut Mobile App
Scan codes directly from your car with the OBDHut app.
Coming Soon
Quick Info
Category
Powertrain
System
Fuel System
Difficulty
Type
Generic (SAE)
Recommended Tools
OBD2 Scanner
A quality scan tool helps you read codes, view live data, and clear faults.
