OBD-II Trouble Codes

P2187 Code: System too Lean at Idle (Bank 1)

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The P2187 code is one of the more ambiguous codes that your vehicle’s onboard diagnostics system can trigger. It’s important to approach diagnosis and repair correctly, so you don’t end up wasting time, energy, and money. This guide will help you learn more about code P2187, including its common causes, symptoms, and the right way to think about diagnosis and repair.

What Does the P2187 Code Mean?

Diagnostic trouble code (DTC) P2187 stands for “System Too Lean at Idle (Bank 1).” It indicates that your vehicle’s computer has detected a potential issue with the fuel mixture at idle. 

The term “bank 1” only applies in vehicles with V-engine and flat layouts. It refers to the side where the number 1 cylinder is located. Note that there is only one bank if your car has a straight engine. 

closeup of car v engine
The term “bank 1” only applies in vehicles with V-engine and flat layouts. It refers to the side where the number 1 cylinder is located.

In an internal combustion engine, the air-fuel mixture is controlled by the powertrain control module (PCM). The PCM uses a closed-loop air-fuel metering system and monitors the heated oxygen sensor signal voltage. It utilizes various data from the sensors in the car, such as the oxygen sensors, manifold absolute pressure (MAP) sensor, mass air flow (MAF) sensor, and crankshaft/camshaft position sensors.

The PCM adjusts the fuel mixture based on the data from the sensors in the car. Its range of adjustments needs to be as precise as possible or else issues like increased fuel consumption or rough idling will happen. 

The PCM will reduce the fuel when the heated oxygen sensor is indicating a rich mixture. Fuel supply will be increased if the heated oxygen sensor signals a lean condition.

The P2187 code is stored when the fuel mixture is too lean—meaning there’s too much air but not enough fuel—at an idle. If you see the code P2189 instead of P2187, the lean fuel trim is in bank 2.

Many owners have reported P2187 for the following makes: Mazda (especially on a Mazda 3), Volkswagen, Audi, Hyundai, and BMW.

Note: The definition of code P2187 may differ depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.

What are the Possible Causes of the P2187 Code?

There’s a long list of causes for code P2187. Take note of the most common reasons why your PCM may be setting this code:

  • Vacuum leak
  • Exhaust leak
  • Faulty sensor 
  • Circuit or wiring issue
  • Fuel delivery problem
  • Engine mechanical issue 
  • An issue with the PCM 
closeup shot of car engine
Engine misfiring? That’s a common symptom of the P2187 code.

What are the Common Symptoms of the P2187 Code?

The possible accompanying symptoms of code P2187 ranges from a mild idle misfire to decreased engine performance. Below are the most common ones you may encounter: 

  • Illuminated check engine light
  • Stalling 
  • Hesitation 
  • Engine misfiring 
  • Erratic engine idling
  • Difficulty starting the engine
  • Hissing or whistling noises from the engine bay

How to Diagnose the P2187 Code

You can watch the video below to get an idea of what diagnosing the code P2187 might involve. Keep in mind that diagnostic and troubleshooting processes may differ depending on the car’s year, make, and model. For instance, the diagnostic process for a P2187 on an Audi won’t be exactly the same as the process for a P2187 on a Mazda, so make sure you’re using references specific to your vehicle.

How to Fix the P2187 Code

Once you’ve established what set off the P2187 code, the next step is to determine the right way to resolve it. Consult online auto repair resources and guides and make sure the solution you come up with is appropriate for your exact vehicle.

If you are not confident with your DIY skills, let automotive professionals resolve the issue. Not only are they well-equipped and well-experienced to fix the P2187 code, but they can also identify and prevent other potential problems in your car.

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic.

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