System too Lean (Bank 2)
The engine control module detected that Bank 2 is running too lean, meaning there's too much air relative to fuel in the combustion mixture. This causes the PCM to add fuel correction, but the system cannot achieve the proper air-fuel ratio despite these adjustments.
What You Might Notice
- Check Engine Light illuminated
- Lack of engine power or acceleration
- Increased fuel consumption
- Spark knock or detonation
- Hesitation or surging during acceleration
Most Common Causes
- 1
Fuel Injector Failure (Bank 2)
A clogged or malfunctioning fuel injector on Bank 2 is not spraying enough fuel into the cylinders. This is the most common cause of lean running conditions on one bank.
- 2
Vacuum Leak
An uncontrolled air leak in the intake manifold or vacuum lines draws extra air into the engine without being measured by the MAF sensor, leaning out the fuel mixture.
- 3
Mass Airflow (MAF) Sensor Malfunction
A dirty or failing MAF sensor provides incorrect air intake readings to the PCM, causing it to calculate an incorrect fuel trim and lean the mixture.
- 4
Failing Fuel Pump or Fuel Pressure Regulator
Low fuel pressure from a weak fuel pump or faulty regulator prevents adequate fuel delivery to the injectors, resulting in a lean condition.
How to Diagnose It
- 1
Check Fuel Injector Failure (Bank 2) — A clogged or malfunctioning fuel injector on Bank 2 is not spraying enough fuel into the cylinders. This is the most common cause of lean running conditions on one bank.
- 2
Check Vacuum Leak — An uncontrolled air leak in the intake manifold or vacuum lines draws extra air into the engine without being measured by the MAF sensor, leaning out the fuel mixture.
- 3
Check Mass Airflow (MAF) Sensor Malfunction — A dirty or failing MAF sensor provides incorrect air intake readings to the PCM, causing it to calculate an incorrect fuel trim and lean the mixture.
- 4
Check Failing Fuel Pump or Fuel Pressure Regulator — Low fuel pressure from a weak fuel pump or faulty regulator prevents adequate fuel delivery to the injectors, resulting in a lean condition.
How to Fix It
- 1
Clean or Replace Fuel Injectors (Bank 2)
Remove and inspect the fuel injectors on Bank 2 (cylinders 3, 5, or 6 depending on engine configuration). Use fuel injector cleaner or have them professionally cleaned; replace if internally damaged or stuck.
- 2
Inspect and Repair Vacuum Leaks
Visually inspect all vacuum hoses, intake manifold gaskets, and PCV system components for cracks or loose connections. Smoke test the intake system to identify leaks and seal or replace damaged components.
- 3
Clean or Replace MAF Sensor
Locate the Mass Airflow sensor in the intake tract and inspect for contamination or carbon buildup. Clean gently with MAF sensor cleaner and a soft brush; replace the sensor if damaged or if cleaning does not resolve the code.
- 4
Test and Replace Fuel Pump or Regulator
Use a fuel pressure gauge to check fuel pressure at idle and under load; compare to manufacturer specifications. Replace the fuel pump or fuel pressure regulator if pressure is below specification.
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