P2187 Diagnostic Trouble Code: System Too Lean at Idle (Bank 1)

Fault code P2187 is called “System Too Lean at Idle (Bank 1)” but in different programs it may be called differently. This fault designation applies to all vehicles equipped with OBD-II.

Technical description and explained code P2187

This Diagnostic Trouble Code (DTC) is a generic powertrain code. Error P2187 is considered a general code because it applies to all makes and models of vehicles. Although the specific repair steps may vary slightly depending on the model.

P2187 Diagnostic Trouble Code: System Too Lean at Idle (Bank 1)

This code is ambiguous, it is not always possible to notice it, because the Check engine indicator may not appear. Therefore, if you do not have a diagnostic scanner, you may not know about it. This code is difficult to crack without a diagnostic strategy. A fuel mixture problem at idle is usually identified when reading other errors with a scanner.

The error code means the fuel mixture is too lean (too much air and not enough fuel) at idle. If you have a 4-cylinder engine, the “Bank 1” information is meaningless to you. However, if you have a 6 or 8 cylinder engine, Bank 1 indicates a problem on the number one side of the cylinder. Code P2189 is the same code, but for Bank 2.

There is an extensive list of components that can cause this error scenario. But with more, the diagnostic procedure is not complicated, just time-consuming. The strategy for finding the error requires that problems be observed and flagged. The check then starts with the most common ones and moves on.

Symptoms of vehicle malfunctions

With a wide range of diagnostics, the listed problems of code P2187 may or may not be present. But it is important here to pay special attention to the observed symptoms. Make notes of what and when the symptoms appear for the diagnostic strategy:

  1. The car stalls at idle.
  2. Difficult to start, especially when it’s hot.
  3. Very irregular idling (floating revs).
  4. Additional codes accompanying error P2187.
  5. Whistling noises.
  6. Lower numbers when the turbo supercharger is running.
  7. Fuel odor.

Factors that can cause this error code

The error code P2187 can mean that one or more of the following problems have occurred:

  • Sensor O₂ (front) is defective.
  • Valve cover seal is worn out.
  • Leaking or loose oil filler cap.
  • Air leaking into the intake manifold after the mass flow sensor due to the manifold itself.
  • Disconnected or cracked vacuum hoses, leak in MAP sensor, leak in turbocharger bypass or it is stuck open.
  • Brake booster hose problem or leak in EVAP system hoses.
  • MAP sensor is defective.
  • EVAP purge valve.
  • Leaking fuel injector.
  • Fuel pressure regulator is defective.
  • Leaking exhaust system.
  • Valve timing system malfunction.
  • ECM (Engine Control Computer) malfunction.
  • Defective heater O₂ (front).
  • Fuel filter is clogged.
  • Fuel pump is worn out and generates low pressure.
  • Mass air flow sensor is defective.

How to fix or reset OBD-2 code P2187

Some suggested steps for troubleshooting and fix the error code P2187:

  1. Check the fuel filler cap for cracks, leaks and proper operation.
  2. Lift the hood and make sure the oil filler cap is tightly closed.
  3. If additional codes were present, start by checking and correcting them.
  4. Look for air leaks, starting with the mass air flow sensor. Check the hose or connection between the sensor and inlet manifold all the way to the manifold. Inspect for cracks or loose connections.
  5. Carefully check all vacuum hoses attached to the intake manifold as well as to the vacuum brake booster. Check the hose to the MAP sensor and all hoses to the turbocharger, if any.
  6. With the engine running, use a carburetor cleaner can. Spray a small amount around the base of the intake manifold. Also at the junction of the two halves if it consists of two parts. Spray around the base of the exhaust gas recirculation for leaks in the manifold. RPMs will increase if a leak is detected.
  7. Check the PCV valve and hose for leaks.
  8. Check the fuel injectors for external fuel leaks.
  9. Inspect the fuel pressure regulator by removing the vacuum hose and shaking it to check for fuel. If it is present, replace it.
  10. Shut off the engine and place a fuel pressure gauge on the Schrader valve on the fuel ramp to the injectors. Start the engine and note the fuel pressure at idle and again at 2500 rpm. Compare these numbers to the reference fuel pressure found online for your vehicle. If the volume or pressure is out of the acceptable range, replace the pump or filter.

Diagnose and repair of problems

The strategy for identifying the malfunction begins with a test drive and observing any symptoms. The next step is to use a code scanner (available at any auto parts store) and scan additional codes.

The P2187 error indicates that the fuel mixture is lean specifically at idle. This is a basic code that can appear due to a variety of components. However, there may be other errors caused by faulty parts.

If the test drive does not cause any symptoms, it may not be a real code. In other words, the fuel mixture is not depleted. And the computer or oxygen sensor is responsible for setting the error code.

Every car has at least two oxygen sensors, one before the catalytic converter and one after the catalytic converter. These sensors signal the amount of free oxygen left in the exhaust after combustion, which determines the fuel ratio.

The front sensor is primarily responsible for the mixture, the second sensor behind the exhaust is used for comparison with the front sensor. To determine if the catalytic converter is working properly.

If floating idle or one of the other symptoms is present, start the process with the most likely cause. Either unmeasured air is flowing into the intake manifold (blow-by, past the sensor), or there is no fuel pressure.

The other components should be checked by a service center that has a Tech 2 scanner and programmer.

On which vehicles does this problem occur most frequently

Fault code P2187 can occur on different vehicles but there are statistics on which brands this occurs most often. Here is a list of some of them:

  • Audi (A4, A5, A6, Q3, Q5)
  • BMW
  • Chery (Tiggo)
  • Chevrolet (Cruze)
  • Ford (Mondeo)
  • Geely (Emgrand)
  • Hyundai (Elantra, Santa Fe, Solaris, Sonata)
  • Kia (Ceed, Cerato, Magentis, Rio, Sorento)
  • Lifan (X60)
  • Mazda (2, 3, 5, 6, CX-7, Demio)
  • Mercedes-Benz
  • Mini (Cooper)
  • Opel (Corsa)
  • Porsche
  • Saab
  • Volkswagen (Passat)
  • Volvo (S80, XC90)
  • Vortex (Estina)
  • LADA (Granta, Kalina, Niva, Priora, Vesta)
  • UAZ (Buhanka, Fermer, Hanter, Patriot)
  • VAZ (2107, 2114, 2115)

Fault code P2187 can sometimes be found with other errors. The most common are the following: P0022, P0026, P0133, P0171, P0174, P0420, P0441, P0507, P2177, P2192, P2279.

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