P0174: System Too Lean (Bank 2)
P0174 is a powertrain diagnostic trouble code in the fuel and air metering group. Our vehicle database stores it against 1 model.
What P0174 actually means
Only 1 model in our database record P0174, a powertrain code in the fuel and air metering group — a narrower fault than the generic codes, which makes the model list below unusually informative.
The stored definition for P0174 is “System Too Lean (Bank 2)”. The first character of the code identifies the system — Powertrain in this case. The second character tells you who defined the code: this one is a generic code defined by SAE J2012 and shared by every manufacturer. Reading the code that way matters: a generic code tests the same underlying condition on almost every vehicle, so the causes below apply broadly across makes.
Within that system, P0174 sits in the fuel and air metering group. That is the part of the vehicle the control module was watching when it set the code — the sensors and actuators that meter fuel and air into the engine — MAF, MAP, oxygen sensors, and coolant temperature — and it narrows down enormously where a technician will start looking. These codes are settled by comparing live sensor readings against specification, which usually takes a scan tool rather than a parts bin.
What makes P0174 easy to get wrong. Bank 2 leans toward causes that affect one bank only: an intake leak on that side, a bank-2 injector, or a dirty MAF that the whole engine shares. Because bank 1 and bank 2 fuel trims are reported separately, comparing the two trims is the fastest way to tell a whole-engine cause from a single-bank one.
How serious is P0174?
We rate P0174 as Moderate — diagnose soon. That rating comes from the severity recorded in our database for this code, not from how alarming the name sounds.
A moderate-severity code usually leaves the vehicle drivable, but the underlying fault tends to worsen and can cascade into a more expensive repair. It is reasonable to drive cautiously to a workshop in the near term, but the code should be diagnosed rather than cleared and forgotten.
Most likely causes of P0174
Our database records 2 causes for P0174, ranked by how many of the 1 model that log this code report each one.
cracked intake tube — recorded on every model that logs this code. Dirty MAF sensor — recorded on every model that logs this code.
Causes are listed as recorded in the database. The same code can have different root causes on different vehicles, so the ranking is a starting order for diagnosis rather than a diagnosis in itself.
How a technician diagnoses P0174
Diagnosis for P0174 follows the same logic as any stored powertrain code: confirm the code is active rather than historic, then work through the ranked causes from cheapest and most likely to most intrusive. In practice that means:
How a technician works P0174 — decision path
Powertrain codes respond to data. Capture the freeze frame, then work through the ranked causes from cheapest and most likely to most intrusive.
- Confirm the code is active and capture freeze-frame dataThe snapshot recorded when the code set holds the engine speed, load, coolant temperature and fuel trims at that moment — often the single most useful piece of evidence for separating one candidate cause from another.
- Compare live data against the freeze frameRe-create the conditions from the snapshot and watch the relevant sensors live. A value that cannot reach the expected range narrows the search immediately.
- Work the ranked causes from cheapest and most likelyThe list on this page is ordered by how many of the recorded vehicles show each cause. Start at the top: an intake leak, a dirty sensor or a worn cap is far more common than a failed assembly.
- Repair the confirmed cause, then re-check the monitorsFix what the evidence actually points at rather than replacing parts speculatively — a misfire or lean code will re-set if the real cause is still present.
- Clear the code and complete a full drive cycleClearing alone proves nothing. The code must stay clear through a drive cycle that reproduces the original conditions, and the readiness monitors must run again.
If a workshop replaces a component for P0174 without showing you the measurement that condemned it, ask for the data. On a fuel and air metering code, the recorded causes are usually testable, so a diagnosis should be demonstrable rather than asserted.
What drives the cost of fixing P0174
We deliberately do not print a single repair price for P0174. Most causes in this group are sensors or wiring, which sit at the lower end of the repair-cost range. The honest answer is that the cost is set by which cause is actually present, and that range is wide — a repair for the first cause listed above and the last can differ by more than an order of magnitude in parts alone: a connector repair and a high-pressure pump are not the same job. Add regional labour rates and the spread becomes wider still.
The factors that actually move the number, in rough order of impact:
- Sensor or circuit. A failed sensor and a broken wire can produce the same reading, so the measurement — not the part counter — condemns one or the other.
- Which sensor it is. An oxygen sensor and a mass airflow sensor sit at very different price points, and both live in this group.
- Access. Some MAP and intake-air sensors sit under the intake manifold, which multiplies labour on an otherwise cheap part.
- Diagnosis billed separately. Shops that credit diagnostic time against the repair change the total more than the part choice does.
The practical approach: get the cause confirmed first, then collect two or three written quotes for that specific repair. To judge whether the repair is worth doing against the value of the vehicle, use our repair-or-replace decision guide.
Vehicles in our database that log P0174
Only 1 model in our database record P0174, so the list below is short but specific. The makes appearing most often are Toyota (1). Each model links to its own guide, where this code appears alongside that vehicle's full fault list and running costs.
Frequently asked questions about P0174
What does the P0174 code mean?
P0174 is a powertrain trouble code meaning "System Too Lean (Bank 2)". It belongs to the fuel and air metering group of the SAE J2012 numbering scheme, and it is a generic code defined by SAE J2012 and shared by every manufacturer. The code is set by the powertrain control module when the monitored system reports a value outside its expected range.
Is it safe to drive with P0174?
Severity for P0174 is rated medium in our database. A moderate-severity code usually leaves the vehicle drivable, but the underlying fault tends to worsen and can cascade into a more expensive repair. It is reasonable to drive cautiously to a workshop in the near term, but the code should be diagnosed rather than cleared and forgotten.
What are the most common causes of P0174?
In our vehicle database, the causes recorded for P0174 are: cracked intake tube; Dirty MAF sensor. They are ranked on the page by how many of the 1 vehicles that log this code list each cause.
How much does it cost to fix P0174?
We do not publish a single figure for P0174 because the real cost depends entirely on which cause is present — a repair for the cheapest cause on the list and the most expensive one differ by an order of magnitude, and labour rates vary by region. The page explains which factors drive the cost and recommends collecting written quotes before authorising work.
Which vehicles commonly report P0174?
Our database stores P0174 against 1 vehicles, most frequently from Toyota (1). The full list is shown on this page and each model links to its own cost and fault guide.
Related codes and next steps
Codes that share the same system group often appear together, because a single fault can set more than one:
For the full list, see the OBD-II fault code cross-reference. If the repair cost is what you are weighing, model the total with our total cost of ownership calculator before deciding, and check whether an open safety recall covers the fault with the recall lookup.
Sources and scope
Code definitions follow SAE J2012 / ISO 15031-6 naming. The descriptions, listed causes, and severity ratings on this page are the values stored in the VehCalc vehicle database (snapshot 2026-08-20) for the models listed above. Codes and causes vary by model year and engine.
Diagnostic reference only — not repair advice. This page is provided for educational and planning purposes and does not replace an inspection by a qualified technician or the manufacturer's service information. Before repairing a vehicle you depend on, confirm the diagnosis with an ASE-certified mechanic.