System Too Lean (Bank 2)

What it means

This appears on engines with two cylinder banks, such as V6 and V8 designs, and means the bank opposite cylinder 1 is running with too much air or too little fuel. The computer has reached its limit adding fuel to compensate.

Symptoms4

• Unsteady idle speed.
• Mild stumbling on acceleration.
• Occasional noticeable loss of power.
• Check engine light on.

Possible causes6

• Intake gasket leak on bank 2.
• Cracked vacuum hose.
• Dirty mass airflow sensor, especially when P0171 is also present.
• Low fuel pressure.
• Partially clogged injectors on bank 2.
• Exhaust leak ahead of the bank 2 oxygen sensor.

How to diagnose and fix6

1. Check whether the code appears alone or with P0171 to tell a bank-specific fault from a shared one.
2. Inspect vacuum hoses and the bank 2 intake gasket.
3. Clean the mass airflow sensor.
4. Request a smoke test for leaks.
5. Measure fuel pressure.
6. Check the exhaust ahead of the bank 2 upstream oxygen sensor.

Repair cost

In Saudi riyals; the highlighted part is the expected range for this fault.

A vacuum leak repair or sensor cleaning is often enough at low cost, rising if intake gaskets or the fuel pump are replaced.

Prices are rough estimates for common cars at independent workshops and vary with the car and the source of the part.

Frequently asked questions