P2189: System Too Lean at Idle (Bank 2)

What it means

Fuel trim on bank 2 hits the lean limit only at idle, while trim returns to normal at higher load. This pattern strongly indicates a vacuum leak — leaks become a larger fraction of total airflow at idle and so dominate the trim, but disappear into background noise above idle.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The engine control module uses oxygen-sensor feedback to adjust fueling for bank 2, the side opposite the cylinder 1 bank on most V engines. P2189 sets when bank 2 fuel trim reaches its lean correction limit at idle but improves above idle, a pattern commonly caused by unmetered air entering that bank at low airflow.

Common causes

Most likely first.

1. Vacuum leak on bank 2
2. PCV valve stuck open

Symptoms

• Check engine light on
• Rough or unstable idle
• Possible hesitation

How to diagnose it

1. Record freeze-frame data and compare bank 2 short- and long-term fuel trims at idle and above idle to confirm the lean correction is mainly an idle condition.
2. Inspect bank 2 intake hoses, manifold connections, and vacuum lines for leaks that admit air downstream of the airflow measurement point.
3. Check the PCV valve and its hoses for a stuck-open path or a leak affecting bank 2.
4. Use an appropriate intake leak test to locate unmetered air around the bank 2 manifold and connected vacuum plumbing.
5. If no leak is found, compare bank 1 and bank 2 sensor feedback and check for an exhaust leak or wiring issue affecting bank 2.

Common fixes

• Replace a split or disconnected bank 2 vacuum or intake hose.
• Repair a leaking bank 2 intake manifold seal or connection.
• Replace a PCV valve that is stuck open and repair its leaking hoses.
• Repair a confirmed bank 2 exhaust leak or sensor circuit fault that is skewing fuel correction.

Can I keep driving?

A short drive may be manageable if the engine runs smoothly, but avoid continued driving if it stalls, hesitates severely, or runs very rough. A persistent lean condition can raise engine temperatures and impair drivability.