P2187 – Meaning, Causes, Symptoms, & Fixes

Code P2187 Definition

Bank 1 has too much air or not enough fuel at idle.

What Does P2187 Mean?

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 P2187 is triggered when this is noticed at idle on bank 1. (4 cylinder engines only have bank 1, if its a “V” configuration engine it is the bank with cylinder 1) The lean condition can be caused by a vacuum leak, which introduces more air into the air-fuel mixture, or by a weak fuel system, which does not input enough fuel into the air-fuel mixture. To keep the engine running properly, the powertrain control module (PCM) tries to compensate for the lean condition by injecting more fuel to the mixture in an effort to maintain the proper 14.7:1 ratio. When these adjustments become too large at idle, code P2187 is triggered.

What Are The Symptoms Of Code P2187?

  • Check Engine Light is on
  • Other codes
  • Lack of power from the engine
  • Rough idle
  • High idle
  • Hard or extended start
  • Engine misfiring
  • Hissing/whistling sound from the engine bay

*No noticeable adverse conditions in some cases

What Is The Cause Of Code P2187?

  • Dirty or faulty mass airflow sensor
  • Vacuum leaks – PCV hoses, vacuum hoses, intake manifold gasket.
  • Oil cap not installed
  • Weak fuel pump
  • Clogged or dirty fuel injectors
  • Clogged fuel filter
  • Exhaust leak
  • Faulty oxygen sensor
  • Faulty air-fuel ratio sensor

How Serious Is Code P2187? – Moderate

It is okay to drive a vehicle with P2187 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. 

Code P2187 Common Diagnosis Mistakes

It is important to complete the entire diagnostic process when diagnosing P2187. Many people will replace the air-fuel sensor or O2 sensor as soon as they get a bad reading, but the root cause is often a dirty or faulty mass air flow sensor or vacuum leak, thus causing the O2 or A/F sensor to read differently to compensate.

Tools Needed to Diagnose:

How To Diagnose And Repair Code P2187?

Difficulty of Diagnosis and Repair (3 out of 5)

  1. Check to see if there are any other codes along with P2187 and clear your Check Engine Light with FIXD. If there are other codes, they may be linked to this concern and should be diagnosed alongside code P2187.
  2. Check the freeze frame data in order to pinpoint the issue.
  3. Check to make sure the engine oil cap is installed and tight.
  4. Inspect all vacuum lines and hoses for leaks, and make sure they are properly connected. If a leak is present, you will hear a hissing sound, though it may be difficult to hear with the engine running. Also, check to make sure the engine oil cap is installed and tight. If you suspect a vacuum leak but are having trouble finding it, check out this detailed guide to finding vacuum leaks.
  5. Reconnect any disconnected vacuum lines and replace any damaged vacuum lines that are leaking, then use FIXD to clear check engine light code P2187. 
  6. If check engine light code P2187 is triggered again, check fuel pressure and compare it to your vehicle’s fuel pressure specification at idle. If it’s low check the fuel pressure regulator to make sure it is properly connected and functioning properly. If it’s functioning normally, replace the fuel pump. 
  7. If your fuel pressure is in spec, remove the mass airflow sensor and clean the sensor using mass air flow cleaner or contact cleaner.
  8. Reinstall the mass airflow sensor and clear the check engine light using FIXD. 
  9. If the check engine light comes back on with code P2187 and you have confirmed there are no vacuum leaks, the mass airflow sensor is clean, and your fuel system is functioning properly, check the exhaust for leaks before the Air Fuel Ratio Sensors or Oxygen sensors. If you find any leaks, have them repaired.
  10. At this point, if the code still persists, you may want to consider replacing your A/F sensor or O2 sensors.

Estimated Cost of Repair

For error code P2187, one or more of the below repairs may be needed to solve the underlying issue. For each possible repair, the estimated cost of repair includes the cost of the relevant parts and the cost of labor required to make the repair. 

  • Vacuum leak $100-$200
  • Clean MAF $100
  • Replace MAF $300
  • Fuel Pump $1300-$1700
  • Fuel pressure regulator $200-$400
  • Exhaust repair $100-$200 (if welded to repair)
  • Air fuel sensor or oxygen sensor $200-$300

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