P0174 Code: The Bank 2 Code That Isn't About Bank 2

OilAndMiles.com - A P0174 code points at one half of your engine, and that's the half you should almost never start with. In the federal complaint record, 11 of the 14 filings naming it name the bank 1 code too, and in the makers’ own bulletins the figure is 168 out of 185.

So the useful question isn't what sits on bank 2. It's what both banks share, which is air on one reading of it and fuel pressure on the other, and three manufacturers have written down which of the two they found.

What does a P0174 code mean?

It means fuel trim hit its limit on bank 2. The computer reads the exhaust, decides the mixture is short of fuel, and adds some. Fuel trim is the name for that correction, and it has a ceiling.

P0174 is the computer telling you it reached that ceiling and the exhaust still reads lean. Your scan tool prints it as system too lean, bank 2, which is the phrase most people search, and if you've typed it as PO174 with a letter O, that's the same code: the first character is a letter, the second is a zero.

Bank 2 is the half of the engine that doesn't contain cylinder 1. On a V6 or V8 that's one cylinder head and its own oxygen sensor, and a four-cylinder engine has one bank and can't set this code at all. That's the whole of what the code names: a side, and a direction.

Which side is bank 2?

Whichever side doesn't have cylinder 1, and it isn't always the passenger side. Where the two banks sit changes from engine to engine, so the only answer that holds everywhere is to find cylinder 1 first, in your owner's manual or the firing order, and take the other head.

On the Honda J35 V6 that puts cylinders 1, 2 and 3 against the firewall, which makes the front bank, the one you can actually reach, bank 2. Our P0430 page draws that engine from above.

It doesn't name a part. Nothing under the hood is called the bank 2 lean part, and the two records below show why looking on that side alone is usually the wrong first move.

Does a P0174 code always come with P0171?

Nearly always, and both records say so. If you've got one of these codes, look for the other before you go looking for a part. P0171 is the same measurement on bank 1, and when the cause is something the two banks share, both codes set within seconds of each other.

We read both records in full, and they agree: this is a pair, not a single code. A 2001 Windstar owner wrote it the way a driver sees it, running lean on right side and left side, which is what the two code numbers mean in plain words.

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So P0174 on its own, with bank 1 reading normally, is the uncommon case. Then the search does narrow to that side, and you're looking at its oxygen sensor, its injectors, and any vacuum line that feeds only those cylinders.

Which cars report a P0174 code?

One 20-year-old minivan carries a third of the federal record. Across every model year, 69 owners filed a complaint naming P0174, and no other vehicle reaches 4. Here's how thin that record is:

• Ford Windstar, 1999 to 2003: 23 of the 69. Owners describe the same repair over and over, intake manifold and valve cover gaskets, and one wrote that gas mileage had fallen to about 10 mpg before the light came on.
• Ford F-150, Chevrolet Silverado 1500 and Toyota Highlander: 3 each. Those are also the three vehicles people search this code with most, and p0174 ford f150 is the busiest of those searches, which is why we priced the parts on these three.
• Only 14 of the 69 are from 2010 or later, the window our other code pages count. This is an older car's code, and the federal record has been thin for fifteen years.

Read that as scope, not as rarity: we count what owners filed, and that's all a complaint record can tell you. A complaint is a federal form somebody chose to fill in, so the record shows what people were angry enough to report, and the Windstar had a gasket problem large enough to make owners ask for a recall.

What are the symptoms of a P0174 code?

Most of the time the light is the symptom. Of the 69 complaints, 32 describe the check engine light and nothing else the driver could feel. What the rest describe, in order:

• Stalling, in 11 of the 69. The most serious thing owners report, and the reason a lean code isn't a wait-and-see item.
• A failed emissions test, in 9. The stored code fails the test on its own, and clearing it leaves the monitors not ready, which fails too. Our P0442 page explains how a station reads that.
• Misfires, in 5. Air without fuel burns badly, and a misfire code such as P0300 often arrives with it.
• Rough idle or lost power, in 9 between them. Worst at idle, because a fixed air leak matters more when the engine is drawing little air.

What does it cost to fix a P0174 code?

From under $10 to over $400, and the cheap end is far more likely. Three parts cover most of what the documents below blame, and you'll pay three times more for the same part on one car than on another.

The gasket is the one to notice. On the Toyota Highlander it's a single gasket under $12, while the Ford F-150 and the Chevy Silverado take a set with a valley pan that reaches $82. The fuel pump runs the other way: $79 on the F-150 and $82 on the Silverado at the cheap end, and on the Highlander the only listing in stock is $428.

On a Toyota, check the VIN before you pay for that pump.

Toyota recalled its fuel pump twice, in campaigns 20V012 and 20V682, covering about 3.4 million vehicles between them. The 2017 to 2019 Highlander is on both lists, with the Camry, Tacoma, Sienna, Tundra, 4Runner and a row of Lexus models, and NHTSA records the consequence as the engine stalling while driving. The remedy is a new pump fitted free at a dealer, so our $428 is what you pay only when the car isn't covered.

That's worth two minutes before any money changes hands, and it's the one thing on this page that can take the repair to nothing.

What should you do about a P0174 code?

Find out whether bank 1 is lean too, before anything is replaced. That one answer decides whether the fault is shared or one-sided. The first two of the 5 steps below cost nothing:

1. Read every stored code, not just this one. Any parts store will do it free, and you don't need a tool of your own. If P0171 is there as well, stop looking at bank 2 as a place.
2. Ask for the fuel trim numbers at idle and at speed. A shop reads them in seconds. If it's lean at idle and improves as the engine speeds up, that's air getting in after the sensor that measures it.
3. Ask for the air sensor to be cleaned and inspected, not replaced. A dirty mass air flow sensor reads low and makes the computer add fuel to both banks, and cleaner costs a few dollars against $22 to $174 for the part.
4. Have the intake checked for leaks before parts are bought. Both banks lean on an older engine is the gasket story the Windstar owners describe, and it's cheaper to find than to guess at.
5. Ask whether a bulletin covers your car. Three makers have published one for this code, and one of them is fixed with software.

And clearing the code isn't the same as the repair working. Once the fault is fixed the computer has to run its own tests again before it reports the system ready, and that takes a mix of driving it can't do standing still. No stored code but a monitor still reading not ready means the car hasn't proved anything yet, which is also why it fails an emissions test in that state and our P0442 page explains what a station sees when it looks.

Common questions

Asked most often

What does a P0174 code mean?

The engine computer added all the fuel it's allowed to add on bank 2 and the exhaust still read lean. Bank 2 is the half of the engine without cylinder 1. The code names a side and a direction, not a part.

Is PO174 the same code?

Yes. PO174 with a letter O is how thousands of people type it every month, and there's no such code: the first character is the letter P for powertrain and the second is the digit zero. Any scan tool will show P0174.

How do I fix a P0174 code?

Start by reading every stored code. If P0171 is there too, the fault is something both banks share, usually an intake leak, the mass air flow sensor or fuel pressure. If P0174 is alone, the search narrows to bank 2's own sensor, injectors and vacuum lines.

What is the difference between P0171 and P0174?

The same measurement on the other half of the engine. P0171 is bank 1, the side with cylinder 1; P0174 is bank 2. In the federal complaint record 11 of the 14 filings naming P0174 name P0171 as well.

Can you drive with a P0174 code?

Usually, for a while, but not indefinitely. Of the 69 complaints on file, 11 describe the car stalling. A lean mixture also runs the engine hotter, and unburned fuel reaching the catalytic converter is what turns a cheap repair into an expensive one.

Will a P0174 code fail an emissions test?

Yes. A stored code fails on its own, and 9 of the 69 complaints describe exactly that. Clearing it before the test doesn't help either, because the readiness monitors then report not ready and the station rejects the car for that instead.

Which cars get P0174 most?

In the federal record, the 1999 to 2003 Ford Windstar: 23 of the 69 complaints ever filed. Ford F-150, Chevrolet Silverado 1500 and Toyota Highlander have 3 each, and they're the three people search this code with most.

Prices are counter prices compiled in September 2026 for the US market: every brand RockAuto lists as fitting each vehicle, cheapest listing per brand. Labor isn't included and we couldn't source it. Prices from $10 up are rounded to the nearest dollar, so $40.79 reads as $41; below $10 they're exact, which is why the Toyota gasket reads $9.68. This article is general information, not advice about your specific vehicle, see the disclaimer.