#lean mixture
4 posts in Car Diagnostics blog about "lean mixture" — OBD-II diagnostics, DTC codes, repair. ← All posts
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P2191 and P2192: system too lean and too rich at higher load
Mixture errors that only appear under load are the ones that hide from an idle test. On a turbocharged engine they usually point at boost, not fuel.
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P2279: intake air system leak — the code that names the fault
Most codes describe a symptom and leave you to find the cause. This one states the cause outright, which makes the search unusually direct.
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P2187 and P2189: system too lean at idle only
A lean condition that exists at idle and vanishes under load points almost exclusively at unmetered air. The load-dependence is the diagnosis, and it costs nothing to observe.
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P0171 and P0174: lean mixture — seven causes, and why the sensor is not one of them
The most common code after misfires. It means the module is adding fuel and still cannot keep up. Seven causes in order of probability, and how to narrow the search using fuel trims alone.