How is fault code P0174 fixed?

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training. 1. Check whether you also have P0171 stored. If both banks are lean, the cause is shared (MAF, fuel pressure, intake gaskets). If only bank 2, the cause is local to that side 2. Bonnet up, engine running, listen and look for vacuum leaks on bank 2's intake plumbing. Spray carb cleaner around suspect joints, if the idle changes, you've found it 3. Inspect the MAF sensor for contamination. Clean it with proper MAF cleaner (never carb cleaner) 4. Check live fuel trim data, long-term trim above +15% on bank 2 confirms the lean condition. If both banks are similar, look at fuel supply 5. Test fuel pressure against the manufacturer's spec 6. Inspect bank 2's exhaust manifold for leaks ahead of the oxygen sensor

System Too Lean (Bank 2)

Jump to the fix

Severity

Medium

Can I keep driving?

Usually drivable, but get it diagnosed without delay.

First step

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training. 1. Check whether you also have P0171 stored. If both banks are lean, the cause is shared (MAF, fuel pressure, intake gaskets). If only bank 2, the cause is local to that side 2. Bonnet up, engine running, listen and look for vacuum leaks on bank 2's intake plumbing.

PPowertrain
0Generic code
1Fuel / Air
74Sequence number

What does it mean?

The long term fuel trim and the short term fuel trim provide essential diagnostic data for diagnosing engine problems. In fact, a scan tool reading of the long term fuel trim can lead to a quick fix of a P0174 or P0171 code. Fuel trims are settings which control the amount of fuel entering the engine to achieve a stoichiometric ratio of 14.7:1. The stoichiometric ratio is the volume mixture of air and fuel that will result in complete combustion of the fuel and oxygen.

The car’s computer control will always seek 14.7 liters of air for each liter of gasoline. It is important to remember this fundamental law for your car. Since the stoichiometric ratio is very important to engine performance, there are multiple air sensors and fuel controls that measure the air and fuel entering your car’s engine.

The most common sensors are the Mass Air Flow sensor (MAF), the Intake Air Temperature sensor (IAT), Manifold Air Pressure sensor (MAP), the Short Term Fuel Trim (STFT), the Long Term Fuel Trim (LTFT), and the Oxygen sensor (02). A few examples will explain the interaction of these sensors and their role in engine diagnosis.

Symptoms

Likely causes

How to fix it

Codes From the Same System

All Fault Codes

Related Similar Codes

This information follows the generic OBD-II definition and does not replace a vehicle-specific diagnosis. The severity rating is rule-based; an authorised diagnostic reading is required for a definitive answer.