What does it mean?
P1150 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Lack of HO2S-21 Switching, Fuel Trim At Rich/Lean Limit .
Symptoms
- Malfunction indicator lamp on with noticeably worse fuel economy
- Rough idle, surging or a stumble under light load
- Reduced power and slow response when pulling away
- Strong exhaust smell, sometimes with a sooty tailpipe on that side
- Fuel trim values on the scan tool sitting at their maximum limits
Likely causes
- Large unmetered air leak on the Bank 2 side, such as a split intake boot or leaking manifold gasket
- Fuel delivery problem on that bank: weak injectors, low rail pressure or a restricted filter
- Front sensor on Bank 2 aged, contaminated or stuck at a fixed value
- Exhaust leak ahead of the sensor holding the reading permanently lean
- Mass air flow sensor drifted, biasing the base fuel calculation for both banks
- Sensor heater not working, so the element never reaches switching temperature
- Wiring fault in the sensor signal or ground circuit flattening the signal
How to fix it
- Read fuel trims for both banks; a limit only on Bank 2 points to a bank-specific fault rather than a global one
- Graph the Bank 2 front sensor and check whether it switches at all when the throttle is snapped
- Smoke test the intake tract on the Bank 2 side and inspect the manifold gasket area
- Check fuel pressure and perform an injector balance test if the trim is positive
- Inspect the exhaust manifold and pipe joints ahead of the sensor for leaks
- Verify sensor heater supply and heater resistance, and check the signal and ground circuits
- Replace the Bank 2 front sensor once air, fuel and wiring have been proven, then reset adaptations and road test