Step 4 of 7 · Check Engine Light Decoded
Lean codes (P0171 / P0174)
Lean codes (P0171 / P0174) — step 4 of 7 in Check Engine Light Decoded. Too much air or too little fuel. After an air-filter job, check the intake boot. A split hose hisses. A dirty MAF can lie.
Free auto & mechanics tip: Lean codes (P0171 / P0174) (step 4 of 7 from "Check Engine Light Decoded").
Too much air or too little fuel. After an air-filter job, check the intake boot. A split hose hisses. A dirty MAF can lie. This is not automatically 'buy injectors'.
A careful look at recent work you did is the first diagnostic step. Vacuum leaks love to appear after someone was in the engine bay.
Pro tip: If you spray anything around boots to find a leak, keep it away from hot exhaust and ignition.
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