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P0174 Diagnostic Trouble Code

Technical description

The engine is running lean on bank 2, meaning the air to fuel ratio is biased towards air.

What P0174 really means

Over time when the engine wears, parts break, or if measuring sensors become faulty, the computer can make corrections by lengthening the on time for the fuel injectors to richen up the mixture. This code can also be accompanied by a P0171, which will identify bank 2 as lean. The ideal stoichiometric ratio is 14.7 parts of air to 1 part of fuel, which allows a good mixture of fuel economy, performance and lower emissions during combustion.

What are the symptoms of a P0174 code?

Generally, a lean code will cause the engine to run poorly, which the driver will notice as a high idle, a misfire, a lack of power, or even engine stalling, and this may happen before the check engine light has turned on. What’s more, these symptoms will be more noticeable at lower speeds and RPMs. The engine can cope with lean problems at higher speeds because demand is so great for air.

What is the severity of a P0174 code?

Critical. A diagnostic check should be run immediately to pin point the exact issue.

What type of repair(s) are needed to resolve a P0174 code?

There is a long list of reasons why the engine runs lean, and a good mechanic needs time to figure out the problem. Unlike rich issues the problem can be on either side of the mixture – too much air or not enough fuel. To be sure, there are some simple answers here – a broken vacuum hose will let in air that the computer cannot account for, or a clogged fuel filter will restrict the supply of fuel. However, plan on dropping off the car and to give sufficient time for the mechanic to figure out the problem.

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What is the cost to resolve a P0174 code?

  • Estimated diagnostic cost: $100
  • Estimated part(s) + labor cost: $50–$800 (depending on diagnosis)
  • Estimated total cost: $150–$900

This code will require a diagnostic check, which will run about $100 depending on the time it takes to find the issue. As there is a laundry list of reasons why the engine runs lean, the average price per repair will vary greatly. You may get lucky with one of the simple repairs mentioned above. A broken vacuum hose sucking in air can be around $50, or a clogged fuel filter for $100. On the other hand, an oxygen sensor or mass air flow sensor can bring a bill of $400 to $500 dollars. A bad fuel pump can be really expensive costing around $600 to $800.

If you vehicle is currently throwing this code, schedule a diagnostic check with a mechanic immediately. Don’t have a regular mechanic? No problem. Compare pricing and schedule an appointment with mechanics in your area with Openbay.

Service article written by an ASE Master Technician

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