P2179: Mixture too lean away from idle (bank 2)

What P2179 means

Above idle, the ECU keeps adding fuel on bank 2 and hits its limit without getting the mixture right. It only appears on V engines or others with two banks. Bank 2 is the side opposite cylinder 1.

Most common causes

• Unmetered air on the bank 2 side (intake gasket, split vacuum hose)
• Dirty or partly blocked bank 2 injectors
• Low fuel pressure from a clogged filter or weak pump
• Dirty mass air flow sensor reading less air than is going in
• Exhaust leak ahead of the bank 2 oxygen sensor
• Bank 2 oxygen sensor giving a false reading

Symptoms

• Engine warning light on
• Lack of power when accelerating or climbing
• Surging at steady speed
• Occasional misfires under load

Can you drive with P2179?

With care You can drive gently, but a lean mixture burns hotter and can lead to misfires. Have it looked at soon.

How to check it

Compare long term fuel trims on both banks live: if only bank 2 is strongly positive, look for an air leak or injectors on that side; if both are high, suspect fuel pressure or the air flow sensor.

How to read and clear P2179 with Final OBD

Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P2179 with this same explanation and whether it’s confirmed, pending or permanent.

With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.

Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.

Similar codes

• P2138 Throttle or pedal position sensors D and E voltage mismatch
• P2146 Fuel injector group A supply voltage circuit or open
• P2177 System too lean off idle (bank 1)
• P2178 Mixture too rich away from idle (bank 1)
• P2187 Mixture too lean at idle (bank 1)
• P2188 Mixture too rich at idle (bank 1)
• P2189 Mixture too lean at idle (bank 2)
• P2191 Mixture too lean at higher load (bank 1)
• P2100 Throttle actuator A control motor circuit open
• P2101 Throttle actuator A control motor circuit range or performance
• P2102 Throttle actuator A control motor circuit low
• P2104 Throttle control system: forced idle

P2179 is a generic code, so it means the same on any make, for example on Alfa Romeo, Dacia, Kia, Nissan, Opel / Vauxhall, Škoda. See what Final OBD does on your car in makes and models.