Cause
Vacuum leak in intake manifold or hoses
Unmetered air entering after the airflow sensor, so the engine receives more air than the module knows about.
A leak is a roughly fixed quantity against an airflow that varies enormously, which is why it dominates at idle and fades as the throttle opens — and why lean codes qualified by engine load point at it so precisely.
Typically a moderate job.
Some of these codes mean you should stop driving
11 of the 45 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (45)
Codes where this is a likely explanation first, rather than merely a possible one.
- P0039 Turbocharger/Supercharger Bypass Valve A Control Circuit Range/Performance Likely for this code Moderate
- P0068 Manifold Absolute Pressure/Mass Air Flow — Throttle Position Correlation Likely for this code Stop driving High
- P0101 Mass or Volume Air Flow Sensor A Circuit Range/Performance Likely for this code High
- P0106 Manifold Absolute Pressure/Barometric Pressure Sensor Circuit Range/Performance Likely for this code High
- P0131 O2 Sensor Circuit Low Voltage — Bank 1 Sensor 1 Likely for this code Moderate
- P0151 O2 Sensor Circuit Low Voltage — Bank 2 Sensor 1 Likely for this code Moderate
- P0170 Fuel Trim Malfunction — Bank 1 Likely for this code High
- P0171 System Too Lean — Bank 1 Likely for this code High
- P0173 Fuel Trim Malfunction — Bank 2 Likely for this code High
- P0174 System Too Lean — Bank 2 Likely for this code High
- P0300 Random/Multiple Cylinder Misfire Detected Likely for this code Stop driving High
- P0505 Idle Air Control System Likely for this code Moderate
- P0507 Idle Air Control System RPM Higher Than Expected Likely for this code Moderate
- P0519 Idle Air Control System Performance Likely for this code Moderate
- P2073 Manifold Absolute Pressure/Mass Air Flow — Throttle Position Correlation at Idle Likely for this code Moderate
- P2177 System Too Lean Off Idle Bank 1 Likely for this code Moderate
- P2179 System Too Lean Off Idle Bank 2 Likely for this code Moderate
- P2187 System Too Lean at Idle Bank 1 Likely for this code Moderate
- P2189 System Too Lean at Idle Bank 2 Likely for this code Moderate
- P219A Bank 1 Air-Fuel Ratio Imbalance Likely for this code Moderate
- P219B Bank 2 Air-Fuel Ratio Imbalance Likely for this code Moderate
- P2339 Cylinder 4 Above Knock/Combustion Vibration Sensor Threshold Likely for this code High
- P0046 Turbocharger/Supercharger Boost Control A Circuit Range/Performance High
- P0065 Air Assisted Injector Control Range/Performance Moderate
- P0069 Manifold Absolute Pressure — Barometric Pressure Correlation Moderate
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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