P1156
PPowertrainUpstream O2 Sensor Stuck Lean (Bank 2)
What does this code mean?
Severity : MediumP1156 is a manufacturer specific code. In the definition used here, it means oxygen sensor HO2S21 (bank 2, upstream) is no longer switching and constantly reports a lean mixture. The exact meaning depends on the manufacturer: on some brands this code refers to a different component.
Symptoms
- Check engine light on.
- Higher fuel consumption.
- Rough idle or hesitation.
- Possible emissions test failure.
Possible causes
- Worn or faulty bank 2 upstream oxygen sensor.
- Intake vacuum leak or exhaust leak ahead of the sensor.
- Damaged sensor wiring or connector.
- Low fuel pressure or dirty injectors on bank 2.
Diagnosis and repair
- Confirm what this code means for your make in the factory information.
- Watch the bank 2 sensor signal in live data.
- Look for vacuum leaks or exhaust leaks.
- Check the wiring, heater circuit and fuel pressure.
- Replace the sensor if it does not switch, then clear the code and road test.
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Code
P1156
Category
Powertrain
Prefix
P
Standard
OBD-II / SAE J2012