P2187 System Too Lean at Idle (Bank 1) DTC

Trouble Code P2187 OBD-II Datasheet

The system is too poor when idle (bank 1)

The P2187 OBD-II DTC indicates that the vehicle's on-board computer has detected a lean mixture at idle in bank 1 or bank 2 (the side of the engine with the corresponding cylinder number, if applicable). A lean mixture means too much air and not enough fuel.

• P2187 - System Too Lean Standby (Bank 1) DTC
• P2187 - System Too Lean at Idle (Bank 1) DTC

What does this mean?

This Diagnostic Trouble Code (DTC) is a generic transmission code. It is considered universal as it applies to all makes and models of cars (1996 and newer), although the specific repair steps may differ slightly depending on the model. We have seen this code on Hyundai, Dodge and other models.

This is an ambiguous code in itself. This code is difficult to crack without a diagnostic strategy. During the last two starts, the ECM detected a problem with the idle fuel mixture.

It looks like the fuel mixture is too lean (too much air and not enough fuel) at idle. If you have a 4 cylinder engine "Bank 1" is meaningless, however if you have a 6 or 8 cylinder engine Bank 1 will be on the number one cylinder side. Code P2189 is the same code, but for bank #2.

There is an extensive list of components that can cause this scenario. For the most part, the diagnostic procedure is simple - just time consuming unless it is checked first. The strategy requires that controllability problems be observed and noted, then start with the most common problems and work your way up.

Symptoms

With a wide range of possibilities, the listed problems may or may not be present. But here it is important to pay special attention to the observed symptoms and make notes about which and when symptoms appear for a diagnostic strategy.

• The car has a malfunction at idle
• Difficult to start, especially when it's hot
• Very irregular idle
• Additional codes to determine the cause of the P2187 source code
• Whistling noises
• Smaller turbo boost numbers
• Fuel smell

Possible Causes of DTC P2187

There are two broad variations that can result in a P2187 OBD-II DTC being logged. Something is letting air into the fuel system or something is restricting fuel flow. The engine control module (ECM) detects a non-ideal fuel mixture and illuminates the Check Engine light on the vehicle's dashboard.

• Defective O2 sensor (front)
• Defective gas cap seal
• Leaky or leaky oil filler cap
• Air leakage into the intake manifold after the MAF sensor due to the manifold itself, a disconnected or cracked vacuum hoses, a leak in the MAP sensor, a leak in the turbocharger bypass or is it stuck open, a brake booster hose or a leak in the EVAP hoses.
• Defective MAP sensor
• EVAP canister purge valve
• Leaking fuel injector
• Defective fuel pressure regulator
• Exhaust leaks
• Malfunction of the variable valve timing system
• Defective ECM (engine control computer)
• Defective O2 heater (front)
• Clogged fuel filter
• The fuel pump wears out and creates low pressure.
• Defective mass air flow sensor

Diagnostic / repair steps

Your strategy for finding this problem 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 get any additional codes.

The computer has set code P2187 to indicate that the fuel mixture is lean at idle speed. This is the basic code, however any faulty component in this cycle that could cause a lean mixture will also be set in the code.

If the test drive shows no symptoms, it may not be the real code. In other words, the fuel mixture is not lean and the computer or oxygen sensor is responsible for setting the code.

Every car has at least two oxygen sensors - one before the catalytic converter and one after the converter. These sensors signal the amount of free oxygen left in the exhaust after ignition, 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 converter is working properly.

If rough idling is present or one of the other symptoms is present, start the process first with the most likely cause. Either unmeasured air is entering the intake manifold or there is no fuel pressure:

• Check the fuel tank cap for cracks, leaks and functionality.
• Raise the hood and make sure the oil filler cap is tightly closed.
• If additional codes were present, start by checking them.
• Look for air leaks starting with the MAF sensor. Check the hose or connection between the sensor and the intake manifold all the way to the manifold for cracks or loose connections. Carefully check all vacuum hoses attached to the intake manifold to connect them to the brake servo. Check the hose to the MAP sensor and all hoses to the turbocharger, if equipped.
• With the engine running, use a can to clean the carburetor and spray a small mist around the base of the intake manifold and where the two halves meet if it is in two parts. Spray the cleaner around the EGR base for leaks into the manifold. RPM will increase if a leak is found.
• Check the tightness of the PCV valve and hose.
• Inspect the fuel injectors for external fuel leaks.
• Inspect the fuel pressure regulator by removing the vacuum hose and shaking it to check for fuel. If so, replace it.
• Stop the engine and install a fuel pressure gauge on the Schrader valve on the fuel rail to the injectors. Start the engine and note the fuel pressure at idle speed and again at 2500 rpm. Compare these numbers with the desired fuel pressure found online for your vehicle. If volume or pressure is out of range, replace pump or filter.

The rest of the components must be checked by a service center that has a Tech 2 scanner and programmer.

Common Mistakes When Diagnosing Code P2187

When troubleshooting a P2187 code, a mechanic should be wary of the following common errors:

• Neglect to clear the DTC after repair
• Neglect to check for code P2187

How serious is the P2187 code?

While it is still possible to drive most vehicles that register code P2187, it is important to address underlying issues as soon as possible. Using the wrong fuel mixture can affect the integrity of other systems and components, leading to more repair costs and frustration than fixing the problem the first time it occurs.

What repairs can fix code P2187?

After a certified mechanic confirms DTC P2187, the following repairs may be required to correct the problem:

• Repair leaks in hoses such as EVAP system hoses or vacuum hoses.
• Elimination of leaks in the exhaust system
• Replacing the fuel filter, fuel pump or fuel pressure regulator
• Replacing fuel tank or oil filler caps
• Replacing O2, MAP or Mass Air Flow Sensors

Additional comments to consider regarding code P2187

As with diagnosing any other OBD-II DTC, this process can take some time due to the possible need for several tests and checks. However, when troubleshooting code P2187, this time can be especially long due to the long list of potential culprits. The problem detection strategy is to move down the list, starting with the most likely cause and moving down to the least common causes.

P2187 System to Lean at Idle Bank 1 "VW 1.8 2.0" How to Fix

Need more help with your p2187 code?

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