P1131
Lack of HO2S Switch - Sensor Indicates Lean (Bank 1 Sensor 1)
This code means the oxygen sensor before the catalytic converter on Bank 1 is consistently reporting a lean air-fuel mixture, and the engine computer isn't seeing it switch back and forth as expected.
Lack of HO2S Switch - Sensor Indicates Lean (Bank 1 Sensor 1)
Common causes
- high
Vacuum Leaks
Leaking vacuum hoses, intake manifold gaskets, or PCV system components can introduce unmetered air, causing a lean condition.
Typical part cost: $0-100 for repair
- medium
Faulty Front Oxygen Sensor (Bank 1 Sensor 1)
The oxygen sensor itself can become slow or faulty, inaccurately reporting a lean condition.
Typical part cost: $80-250 part
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First things to check
- 1Check for vacuum leaks using a smoke machine or by listening for hissing sounds around the intake manifold and vacuum lines.
- 2Inspect the air intake system for leaks or restrictions (e.g., cracked intake tube, dirty air filter).
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Related codes
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Frequently asked questions
What does 'lean' mean for an engine?
A 'lean' condition means there's too much air and not enough fuel in the air-fuel mixture entering the engine. This can cause the engine to run hotter, reduce power, and potentially lead to engine damage.
Is P1131 the same as P0171?
They are very similar and often appear together. P0171 indicates a general 'System Too Lean (Bank 1)' condition, while P1131 specifically points to the upstream oxygen sensor on Bank 1 indicating a lean condition and not switching properly, often as a result of the P0171 condition.
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