P0171, P0174 GM vehicles? (Correct answer)

  • P0171 and P0174 occur when the air/fuel mixture on the vehicle gets too lean. They are both thrown when the oxygen sensors detect that there is not enough oxygen in the exhaust. The engine then makes adjustments to compensate and throws these codes, which trigger the service engine soon light.

What causes P0171 and P0174 codes Chevy?

A P0171 or P0174 trouble code can happen because of a vacuum leak or faulty sensor. Vacuum leak faults usually—not always—manifest more readily at lower speeds; as a rough idle, for example. A capable scan tool can check fuel trim values at idle and at higher engine speeds and detect when the lean condition occurs.

How do I fix my GM code P0171?

Remove the mass air flow sensor and clean the sensor using mass air flow cleaner or contact cleaner. Reinstall the mass air flow sensor and clear the check engine light using FIXD. If the check engine light comes back on with code P0171 continue the diagnostic process.

Can a bad PCV valve cause code P0171?

The most common causes of the P0171 code are vacuum or intake leaks, low fuel pressure, faulty PCV valve, or a faulty MAF sensor. Other things can also cause the P0171 code.

Can a dirty air filter cause a P0174 code?

A plugged Fuel Filter or poorly functioning Fuel Pump can set the P0174 code. The computer hears (accurately) from the Oxygen Sensor that the Fuel Mixture is too lean so the computer keeps increasing the amount of fuel being delivered into the combustion chambers.

What is a P0171 code for a Chevy?

What Does P0171 Mean For Your Chevrolet? Combustion engines run most efficiently when they maintain an air-fuel mixture ratio of 14.7 parts air to 1 part fuel. When there are more than 14.7 parts air to 1 part fuel in the air-fuel mixture, a lean condition exists and code P0171 is triggered.

Can a dirty air filter cause a P0171 code?

If the filter is clogged or excessively dirty, this is enough to impede or restrict the air flow, hence resulting in a lean running condition. Besides a dirty air filter, the P0171 code can also be blamed on a dirty or faulty MAF sensor and a clogged fuel filter.

Can you drive with a po171 code?

It is okay to drive a vehicle with P0171 for a short period of time, but driving with this code for an extended period of time can overheat the engine and cause internal engine damage.

What does code 171 mean?

What the P0171 code means. The P0171 OBD-II code means that, on the first bank of the engine, the fuel system is running weak or a vacuum leak exists near this side of the engine. A lean condition occurs when the engine either receives too little fuel or too much air.

Can a bad O2 sensor cause P0171?

A P0171 or P0174 lean code with an O2 sensor reading lean all the time mean — well, several things. The real problem may not be a bad O2 sensor, but possibly be an engine vacuum leak, low fuel pressure or dirty fuel injectors that are causing the engine run lean.

Is it bad for an engine to run lean?

In combustion engines, ‘ running lean’ goes beyond using gas efficiently. In effect, that status makes the engine perform with less gasoline than it needs to operate properly, and it increase the amount of friction between the engine’s moving parts. Running lean can damage an engine.

Can bad spark plugs cause P0171?

Not likely. A P0171 ( too lean, Bank 1 ) code is most often caused by a vacuum leak downstream from the MAF sensor or a malfunctioning MAF sensor. Bad spark plugs could actually cause the opposite code ( too rich, bank 1).

What are the signs of a bad pcv valve?

Bad PCV Valve Symptoms

  • Check Engine Light. The most common and most noticeable sign of all bad PCV valve symptoms is probably a check engine light on your dashboard.
  • High Idle RPM/Rough Idle.
  • Lean/Rich Mixture.
  • Misfires.
  • Rough Acceleration.
  • Increased Oil Consumption & Oil leaks.
  • White/Black/Blue Smoke from the Exhaust.

Can an exhaust leak cause a P0171 code?

An exhaust leak upstream of the O2 is kind of unlikely to cause a p0171, as it would have to be siphoning ‘clean’ air in via venturi effect. A head gasket leak or cracked head will allow the coolant to be burned.

P0171, P0174 GM vehicles

The General Motors Company has released service bulletinPIP5549 to resolve problem codes P0171 and P0174 on the GM vehicles indicated in the table below.

Vehicles affected

Buick Enclave model years 2012-2018 Cadillac XTS 2015-2018 with 3.6LLT and 3.6LFY engines Chevrolet Colorado (2015-2016) 3.6 LFXl Chevrolet Colorado Chevrolet Equinox 2015-2017, 3.6 LFX, 3.6 LFX Chevrolet Impala 2015-2018, 3.6 LFX Chevrolet Traverse 2012-2018, 3.6 LFX Acadia 3.6 LFX and 3.6 LFYGMC from 2012 to 2017. Canyon 2015-2016 3.6 LLTGMC Canyon GMC Terrain 2015-2017 (3.6 LFXGMC Terrain) 3.6 LFX (Low-Frequency Excitation)

See also:  Brake lights don't work? (TOP 5 Tips)

Cause of P0171, P0174 and check engine light

P0171 and P0174 codes have been identified as being caused by a vacuum leak in the foul air tube, intake manifold, or purge valve, according to General Motors (GM).

Diagnose P0171, P0174

P0171 and P0174 codes may be caused by a vacuum leak in the foul air tube, intake manifold, or purge valve, according to General Motors.

Purge Valve Test

1. Remove the plugs and reinstall the foul air tube to the manifold in the reverse order of removal. 2. Disconnect the vacuum hose from the purge valve as well as the power supply. 3. Restart the car, then place your finger over the open port on the purge valve to prevent it from closing. 4. If you sense a suction on the valve port, the valve is leaking and must be replaced immediately. Restart the car and then reinstall any detachable components. Please refer to the corresponding diagnostic method in your shop manual if there is no suction sensed at the valve port.

Part 1 -Troubleshooting P0171 and P0174 (GM 4.3L, 5.0L, 5.7L)

The date was June 19, 2011. On January 29, 2020, the information was updated. Contributed by:Abraham Torres-Arredondo 214 is the article ID number. It might be difficult to determine the cause of diagnostic issue codes P0171 (System Too Lean Bank 1) and/or P0174 (System Too Lean Bank 2). Why? This is due to the fact that these classifications do not single out any individual part as being faulty. The purpose of this post is to simplify the process of diagnosing these two codes on the GM 4.3, 5.0, and 5.7-liter engines.

This tutorial may be found in Spanish at the following link: Cómo Probar: Códigos P0171 y P0174 (GM 4.3L, 5.0L, 5.7L) (at:autotecnico-online.com).

Important Suggestions And Tips

TIP 1: In order to fully benefit from the tests and suggestions in this article, you’ll need a scan tool to do so (that has Live Data capability). A professional technical level scan tool is not required, since a generic scan tool with Live Data capabilities would suffice (don’t have a scan tool? Purchase one here). Do you require a scanning tool? Visit this site for my recommended scanner: Actron CP9580 Scan Tool. TIP 2: Some of my testing recommendations include testing while the engine is running, which means you’ll be on your toes and aware the entire time.

P0171 And P0174 Essentials

TIP 1: A scan tool is required in order to fully benefit from the tests and suggestions in this article (that has Live Data capability). A professional technician level scan tool is not required, as a generic scan tool with Live Data capability will suffice. (Don’t have a scan tool?

A scan tool may be required in your situation. Visit this site for my top recommendation: Actron CP9580 Scan Tool. A second piece of advice is to conduct some of your testing while the engine is running. This will keep you alert and on your toes. Always keep your focus on safety.

  1. An extreme Lean situation has been identified by the PCM, as indicated by this DTC. For the uninitiated, this simply implies that the PCM has detected a vacuum leak (which might be genuine or imagined)
  2. When the vacuum leak is detected, the PCM reacts by pumping the maximum quantity of fuel permitted (under its program) into the cylinders of Bank 1 in order to compensate for it.

Lean Bank 2 of the Fuel Trim System (P0174) (System Too Lean Bank 2)

  1. An extreme Lean situation has been identified by the PCM, as indicated by this DTC. For the uninitiated, this simply implies that the PCM has detected a vacuum leak (which might be genuine or imagined)
  2. To compensate for the vacuum leak, the PCM reacts by pumping the maximum quantity of fuel permitted (under its program) into the cylinders of Bank 2 to compensate for the vacuum loss.

When it comes to dealing with these two diagnostic issue codes, the fact that they don’t point the finger at a specific sensor or component is a major source of frustration for you and me. For example, neither of the two codes above indicates that the oxygen sensors are malfunctioning. In other words, the computer is having difficulty estimating the amount of gasoline it can spray into the engine since there is an unknown amount of air entering the engine. Because of this, no matter how much gasoline it puts (into the engine), it will never make up for lost time (usually, but not always, due to a very large vacuum leak).

See also:  Fix P0171 code, P0174 code? (Correct answer)

It might be an oxygen sensor that is beginning to fail but has not yet failed entirely, or it could be a very filthy MAF sensor that is causing the problem.

Where Are Bank 1 And Bank 2?

Before I go into specific testing strategies for troubleshooting a P0171 or a P0174, allow me to explain what Bank 1 and Bank 2 are in more depth. As previously stated, these codes indicate that the PCM (Powertrain Control Module= Fuel Injection Computer) has detected that it is required to dump more fuel than necessary in order to correct for a real or perceived vacuum leak that is impacting a specific bank of cylinders. Bank 1: Now, to be a bit more explicit, the P0171 DTC informs you that bank 1 is the one experiencing difficulties.

  • Cylinders 1, 3, 5, and 7 are the most important (V8 5.0L, 5.7L).
  • Bank 2: A P0174 DTC informs you that bank 2 is the one experiencing difficulties.
  • Cylinders 2, 4, 6, and 8 are the most important (V8 5.0L, 5.7L).
  • The pre catalytic converter oxygen sensors are the primary sensors responsible for informing the PCM when there is an issue with the air fuel combination.

What Do P0171 and PO174 Mean?

The code P0171 indicates that the fuel mixture in Bank 1 of the engine is too lean. P0174 indicates that the fuel mixture in Bank 2 of the engine is too lean. Engine Cylinder 1 is located on the same side of the engine as Engine Bank 1. Engine Bank 2 is located on the opposite side of the engine from Engine Bank 1. It may be necessary to consult a firing order and cylinder placement diagram in order to determine whether side of the engine is Bank 1 or Bank 2. P0171 is activated by the ‘upstream’ oxygen sensor in engine bank 1, and P0174 is triggered by the ‘upstream’ oxygen sensor in engine bank 2, respectively.

  • The symptoms and causes will assist you in determining the specific nature of the problem and how to resolve it.
  • Upstream sensors, or those located close to the engine and before the catalytic converter, are referred to as Sensor 1.
  • These upstream sensors check that the proper air/fuel ratio is being introduced into the engine cylinders by detecting the oxygen levels in the exhaust gases that are being expelled from the engine.
  • A high voltage measurement that remains constant suggests a rich fuel combination with insufficient oxygen.
  • In this case, the ideal ratio is 14.7:1.
  • A P0171 or P0174 error code is generated when your powertrain/engine control module receives a measurement that indicates there is too much oxygen present and the ratio is improper.
  • It is crucial to note that the very nature of the oxygen sensor delivering these codes, in the absence of any other oxygen sensor failure codes, indicates that the sensor is functioning as it should be.

Because this code appears by itself, it is difficult to determine whether or not a monitored component has failed, because if there is, the code would be sent to that component as well. In a nutshell, the engine is running lean, and the computer is unable to determine why.

P0171 and P0174 Symptoms

There are several cases where engine performance concerns do not manifest themselves. Some lean circumstances, on the other hand, might cause your car to have the following performance issues:

  • In many cases, engine performance concerns do not manifest themselves on the surface. A vehicle’s performance might be negatively affected by lean conditions in certain instances.

Most of the time, you’ll only get notified if there’s a lighted CEL in the vicinity. Look for one of these typical reasons to figure out how to fix the problem code you’re having. The first thing to check is whether or not there are any additional codes present. If either code (or both codes) come at the same time as, for example, a Mass Airflow Sensorcode, it is reasonable to believe that the MAF sensor is the source of the lean state in question. Unless one of the codes (P0171 or P0174) appears by itself, or if both codes are saved, you have an issue that necessitates more detective work.

Common Causes

There are a variety of minor and significant fixes that might result in this problem. Start with the simplest difficulties and work your way through the list until you’ve identified the root cause of your error code. Lean situations are frequently created by air entering the system in an area where it cannot be seen or measured. The intake system, which is normally behind the MAF sensor, and a vacuum leak anywhere in the intake system are the two most likely culprits for this. Starting with the intake boot that connects the MAF to the throttle body, look for any leaks.

  1. Check all of the vacuum hoses on the engine for cracks or breaks in the hose before continuing.
  2. This is a common sign of a large vacuum leak and should be addressed immediately.
  3. If nothing appears to be wrong here, it is possible that there are other, more serious problems going on.
  4. This will result in a significant vacuum leak and the onset of a lean situation.
  5. It is crucial to remember that, in most cases, fuel-related difficulties such as these will also result in a misfire code being displayed – either randomly or on specific cylinders.
See also:  Car smoking from under the hood? (Correct answer)

How to Fix P0171 and P0174

Minor or large repairs might be the source of this problem in many cases. Work your way through the simplest difficulties first, then progress to the more difficult ones until you have determined the source of your problem code. Low-pressure circumstances are frequently generated by air entering the system in an area where it cannot be detected. The intake system, which is normally behind the MAF sensor, and a vacuum leak anywhere in the intake system are the two most likely culprits for this problem.

  • Cracks, loosened hose clamps, and any other openings where air may get in should all be checked out.
  • During operation of the engine, pay close attention to the sound of air being sucked through a break, since this might indicate a large vacuum leak.
  • The possibility of additional serious concerns developing if nothing appears in this section should not be overlooked.
  • Due to the vacuum leak, the system will get overloaded and go into lean mode.

However, it is crucial to understand that, in most cases, fuel-related problems such as these will also result in a misfire code being displayed — either randomly or on specific cylinders.

P0171 and P0174 Codes

The following 42 minutes ago, Chuck L stated: FYI: I had a collapsed AFM lifter and had to remove the entire top of the motor (including the heads) and replace all of the lifters. I purchased a package that had the lifters as well as all of the gaskets. Did you completely remove AFM or did you only replace both the regular and De-Ac lifters with new ones? If the latter is the case, you must also replace the VLOM, since this is standard operating procedure, or you will have to purchase new lifters.

  1. You’ll need a scan tool with graphing capabilities, such as the Tech-2.
  2. First, make sure your grounds are secure and your battery is in good working order.
  3. Keep an eye on the performance of your downstream O2 sensors in relation to the cats; if they behave in the same manner as the upstream sensors, it’s time to replace them.
  4. Magnaflow’s were used in place of mine.
  5. In 2011, a new driver’s side valve cover was introduced, with the entrance for the PCV ‘valve’ being moved to the left.
  6. LY5, LMG, LC9, or something else?

PO171 and PO174 Check Engine Codes

I looked around and didn’t find anything particular, so I’ll just go ahead and say it. The truck is a 2016 Canyon 4×4 with the 3.6L engine and around 94K miles on it. Engine codes PO171 and PO174 have been appearing on my dashboard for the last two weeks now. They return a day or two after I have removed them out of my house. I’ve noticed that it appears to happen when I’m at a stoplight. She starts out with a harsh idle, almost as if she’s ready to shut down, but then she settles down to a regular idle and the check engine light illuminates.

According to the internet, these codes are caused by a ‘lean mixing’ problem that might be caused by up to 12 different factors.

When I opened the gas cap the last three or four times I went to get gas, I heard an intake of air sound coming from the engine.

In addition, the truck has begun to shut down around halfway through the filling process.

In the past, I have never experienced this issue.

Has anyone else had this problem? I don’t want to start replacing components and hoping that the replacement is the correct one. I’d also like the remote start to function again, because it’s getting chilly here in North Carolina, lol. Please accept my thanks in advance.

Leave a Comment

Your email address will not be published. Required fields are marked *