Ageing or contaminated Bank 2 Sensor 1 oxygen sensor responding slowly; Damaged wiring, poor connector contact or corrosion in the sensor circuit; Exhaust leak near the Bank 2 sensor letting in false air and distorting readings; Sensor heater circuit fault or heater relay/supply problem slowing sensor warm-up; Contamination from oil, coolant or silicone entering the exhaust, coating the sensor; Underlying fuelling or air metering fault on Bank 2 (for example a vacuum leak or leaking injector); Fault in the engine control unit's sensor input.

P1179

O2 Sensor Signal Circuit Slow Switching From Rich to Lean Bank 2 Sensor 1.

BMW
Powertrain
Manufacturer code
Low severity

How this code is built

P: SystemPowertrain
1: Defined byThe manufacturer
1: AreaFuel and air metering
79: FaultThe specific fault in that area

What it means

On BMW, P1179 means the engine control unit saw the Bank 2 Sensor 1 oxygen sensor (upstream of the catalytic converter) switching slowly from rich to lean. A healthy sensor flips quickly between rich and lean as the fuel control cycles, so a sluggish response suggests the sensor is ageing or contaminated, or that something is distorting its signal. The exact sensor type and bank layout depend on the model and engine.

Symptoms

Engine warning light on
Slightly higher fuel consumption
Rough or unsteady idle in some cases
Poor throttle response or hesitation
Failed emissions test
Fuel trims drifting away from normal

Possible causes

Ageing or contaminated Bank 2 Sensor 1 oxygen sensor responding slowlylikely
Damaged wiring, poor connector contact or corrosion in the sensor circuitpossible
Exhaust leak near the Bank 2 sensor letting in false air and distorting readingspossible
Sensor heater circuit fault or heater relay/supply problem slowing sensor warm-uppossible
Contamination from oil, coolant or silicone entering the exhaust, coating the sensorrare
Underlying fuelling or air metering fault on Bank 2 (for example a vacuum leak or leaking injector)possible
Fault in the engine control unit's sensor inputrare

How to diagnose

Read all stored and pending fault codes and note any related fuel trim, misfire, heater or other oxygen sensor codes.
Review freeze frame data for engine temperature, load and speed when the code set.
Inspect the Bank 2 Sensor 1 wiring and connector for chafing, heat damage, water ingress and corrosion.
Check the exhaust upstream of the sensor, including manifold and joints, for leaks or blowing gaskets.
Check for vacuum or intake air leaks and compare short and long term fuel trims between banks.
With live data, watch the Bank 2 Sensor 1 signal at operating temperature and compare its switching speed with Bank 1 Sensor 1.
Check the sensor heater circuit supply and resistance against the manufacturer's specification for your model.
Look for signs of oil or coolant consumption that could contaminate the sensor.

How to fix

Replace the Bank 2 Sensor 1 oxygen sensor if live data and tests show it is slow or out of specification.
Repair or replace damaged wiring or connectors in the sensor circuit.
Repair exhaust leaks upstream of the sensor and renew any faulty gaskets.
Fix any vacuum leaks or fuelling faults found on Bank 2, then recheck fuel trims.
Repair the heater circuit supply or relay fault if one is found.
Clear the codes after repair and road test to confirm the fault does not return.

Can I keep driving?

Low severity

The car can normally be driven while you book it in, as this is mainly an emissions and fuel economy concern. Do not leave it for long, as a poorly controlled mixture can increase fuel use and may eventually stress the catalytic converter.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.