P0174 means system too lean bank 2: on a V6, V8 or flat engine, the bank without cylinder 1 is getting more air than the fuel system can match, and fuel trim has hit its limit. If P0171 is set too, look for one cause both banks share - a dirty MAF sensor, low fuel pressure or a large vacuum leak. P0174 alone points to a leak, injector or exhaust leak on that bank.
Also written as PO174 or P174.
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P0174 is the bank 2 counterpart to P0171 and appears on V6 and V8 engines. Bank 2 is running lean - too much air for the amount of fuel. When P0171 and P0174 appear together, the cause is usually something common to both banks, such as a dirty MAF sensor, a weak fuel pump, or a large vacuum leak, rather than a single injector or gasket.
Yes for a short trip, though it is worth fixing soon rather than ignoring. Like P0171, a lean condition mostly causes rough idle, hesitation, and mildly reduced power rather than a breakdown. Left unaddressed for weeks or months, running lean on bank 2 can eventually cause misfires or added engine wear, so get it diagnosed within a couple of weeks - especially if P0171 is set alongside it, which points at something shared between both banks.
Listed roughly most-likely first. Confirm with a scan tool and the freeze-frame data before replacing parts.
| Fix | DIY parts | At a shop |
|---|---|---|
| Clean or replace the MAF sensor | $10 - $150 | $50 - $250 |
| Smoke-test and seal a vacuum leak on bank 2 | $10 - $50 | $100 - $300 |
| Replace a weak fuel pump or filter | $80 - $300 | $300 - $600 |
Ranges are rounded and for the US market only - actual price depends on region, shop labor rates, and the exact make and model.
What a new MAF sensor costs, if testing points to it
These open an Amazon search - add your year, make and model, because most of these parts are fitment-specific.
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P0174 is a lean condition on bank 2, and it only exists on engines with two cylinder banks - V6, V8, and flat layouts. Its real diagnostic value comes from what it appears alongside. On its own, it points at something specific to bank 2: one manifold gasket, one bank of injectors, one vacuum line. Paired with P0171 on bank 1, both banks are lean, which redirects you entirely toward something shared - the mass airflow sensor, fuel supply, or a leak at a central point both banks depend on.
Treating this as a bank 2 hardware problem without first checking whether bank 1 is also lean wastes a lot of effort in the worst-access part of the engine. If both banks are lean, nothing on bank 2 is at fault and you are looking in the wrong place entirely.
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Difficulty: Moderate. Time: 1 - 4 hours. DIY parts: $20 - $280. Shop total: $150 - $700.
The diagnosis is genuinely easier than the single-bank equivalent, because bank 1 gives you a healthy reference to compare against. The physical work is harder, since bank 2 on a transverse V engine is the side crammed against the firewall. Do the comparison yourself to know exactly what is wrong, then decide whether you want to be the one reaching back there.
Replace vacuum and breather hoses proactively on V engines. The plastic and rubber fittings on the hot, cramped rear bank harden faster than anything on the front. They are inexpensive parts guarding against a diagnosis that is expensive purely because of where it lives. Log hose and gasket work in ServiceSage with mileage, so when the front bank eventually follows the rear you already know what was done and when. Track this maintenance free.
Typical US independent-shop repair cost for P0174 runs about $100 - $600, depending on the root cause. Common fixes: Clean or replace the MAF sensor (about $50 - $250 at a shop); Smoke-test and seal a vacuum leak on bank 2 (about $100 - $300 at a shop); Replace a weak fuel pump or filter (about $300 - $600 at a shop).
No, not on its own. P0174 will keep coming back every time the relevant monitor re-runs until the underlying cause is actually repaired - clearing it with a scan tool without fixing what triggered it only delays the light coming back on.
It is the full name of P0174. Lean means there is more air than fuel for the amount of air the computer measured. The computer trims fuel up to correct it; when it has added as much as it is allowed to on bank 2 and the mixture is still lean, it sets P0174. Bank 2 is the side of a V or flat engine that does not contain cylinder 1 - an inline four-cylinder has no bank 2, so it cannot set this code.
That the cause is on bank 2 only: an intake gasket or vacuum fitting on that side, a breather hose on that bank, a bank 2 injector, or an exhaust leak ahead of the bank 2 upstream oxygen sensor. Compare the long-term fuel trims of the two banks on a scan tool - if only bank 2 is high, keep looking on that side; if both are high, look at what feeds both banks.
Related trouble codes: P0171 - System Too Lean, Bank 1, P0101 - Mass Air Flow (MAF) Sensor Circuit Range/Performance, P0172 - System Too Rich, Bank 1, P0113 - Intake Air Temperature (IAT) Sensor 1 Circuit High, P0087 - Fuel Rail / System Pressure Too Low