P219B: Bank 2 Air-Fuel Ratio Imbalance

What it means

The engine control module detects an air-fuel ratio imbalance on bank 2. The code does not identify a particular cylinder or establish the cause.

At a glance

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

How it works

Bank 2 is the cylinder bank opposite the one containing cylinder 1, and the control module uses combustion and exhaust feedback to assess its air-fuel balance. P219B sets when it detects an imbalance on bank 2. The code does not single out a cylinder or establish whether a fuel, air, ignition, compression, or sensor issue is responsible.

Common causes

Most likely first.

1. Clogged, leaking, or faulty fuel injector on bank 2
2. Intake or vacuum leak affecting a cylinder on bank 2
3. Ignition misfire or weak spark on bank 2
4. Uneven compression on a cylinder in bank 2

Symptoms

• Check engine light on
• Rough idle or engine vibration
• Hesitation or uneven acceleration
• Reduced fuel economy

How to diagnose it

1. Read freeze-frame data and compare bank 2 fuel trims and misfire counts with bank 1 to identify when the imbalance appears and whether bank 2 differs.
2. Inspect bank 2 intake runners and nearby hoses for leaks that could affect a cylinder on that bank.
3. Check bank 2 injectors for restricted flow, leakage, or uneven contribution using suitable test data.
4. Inspect ignition components on bank 2 and look for misfires that could distort the air-fuel balance assessment.
5. If those checks do not reveal a cause, compare compression among bank 2 cylinders and verify relevant sensor inputs against the manufacturer’s specification.

Common fixes

• Repair an intake or vacuum leak affecting a bank 2 runner.
• Clean or replace a bank 2 injector confirmed to be restricted or leaking.
• Repair a bank 2 ignition fault causing uneven combustion.
• Address low compression on the affected bank 2 cylinder if confirmed by testing.

Can I keep driving?

If the light is steady and the engine runs smoothly, drive gently and arrange diagnosis soon because continued imbalance can worsen fuel economy and emissions. Stop driving if the light flashes, vibration becomes severe, or power falls noticeably.