<ul> <li><b>Engine Light ON (or Service Engine Soon Warning Light)</b>: The illumination of the engine light indicates that the ECU has detected a lean condition in Bank 1 during high load. This could be due to <causes> such as a vacuum leak, faulty fuel injectors, or a malfunctioning mass airflow sensor.</li> <li><b>Poor Engine Performance</b>: The vehicle may experience reduced power and acceleration due to the lean air-fuel mixture. Potential <causes> include a clogged fuel filter, low fuel pressure, or a failing fuel pump.</li> <li><b>Rough Idle</b>: A lean condition can cause the engine to idle roughly, which may be due to <causes> such as intake manifold leaks or issues with the oxygen sensor.</li> <li><b>Increased Fuel Consumption</b>: The engine may compensate for the lean condition by injecting more fuel, leading to higher fuel consumption. This could be caused by <causes> like a faulty fuel pressure regulator or a dirty air filter.</li> </ul>

<ul><li>Fuel injectors may not be delivering the correct amount of fuel, causing a lean condition.</li><li>The Mass Air Flow (MAF) sensor might be providing incorrect air intake readings, leading to improper fuel mixture.</li><li>Low fuel pressure can result in insufficient fuel delivery to the engine, causing a lean mixture.</li><li>The front Heated Oxygen Sensor (HO2S) may be malfunctioning, providing inaccurate data to the ECU.</li><li>An exhaust system leak can introduce extra oxygen, skewing the air-fuel ratio.</li><li>A faulty Positive Crankcase Ventilation (PCV) system can cause unmetered air to enter the intake manifold, leading to a lean condition.</li></ul>

<ul> <li><b>Check for Technical Service Bulletins (TSB)</b>: Verify if there are any TSBs related to this issue for your vehicle. This can provide known fixes and save diagnostic time.</li> <li><b>Inspect for Additional DTCs</b>: Check for any other diagnostic fault codes, especially those related to the fuel system. Diagnose and resolve these codes first to avoid misdiagnosis.</li> <li><b>Inspect for Intake and Exhaust Leaks</b>: Ensure there are no intake or exhaust leaks. An intake leak can cause a lean condition, while an exhaust leak can give a false lean reading.</li> <li><b>Locate and Inspect Sensors</b>: Locate the air/fuel ratio sensor/oxygen sensor and the mass airflow (MAF) sensor. Visually inspect connectors and wiring for damage, corrosion, or burn spots.</li> <li><b>Clean Sensor Connectors</b>: If necessary, clean the sensor connectors using electrical contact cleaner or 91% rubbing alcohol and a plastic bristle brush. Apply dielectric silicone compound to the terminals.</li> <li><b>Clear DTCs and Retest</b>: Clear the diagnostic trouble codes from memory using a scan tool and see if the code returns. If it does not, the issue was likely with the connections.</li> <li><b>Test MAF Sensor Voltage</b>: Monitor the MAF sensor voltage using a scan tool or DVOM. The voltage should increase with engine RPM. Compare readings to manufacturer specifications. Replace the MAF sensor if it fails this test.</li> <li><b>Monitor AFR/O2 Sensor</b>: If the code persists, monitor the air/fuel ratio sensor/oxygen sensor. If it indicates a lean condition, investigate potential causes such as intake/exhaust leaks, fuel system issues, or EVAP system faults.</li> <li><b>Inspect Fuel System Components</b>: Check the fuel pressure, fuel pressure regulator, fuel pressure sensor, and fuel injectors for proper operation. Replace any faulty components.</li> <li><b>Evaluate EVAP System</b>: Inspect the EVAP system, including the canister purge regulator valve, for any issues that could cause a lean condition.</li> <li><b>Consider PCM Issues</b>: If all other components are functioning correctly and the code persists, consider the possibility of a PCM fault. Ensure all other potential issues have been eliminated before suspecting the PCM.</li></ul>

<p>The DTC code P2191 indicates that the air-fuel mixture is too lean at higher loads in Bank 1. This is a critical issue as it can lead to engine misfires, increased emissions, and potential engine damage.</p><ul><li><b>Immediate Actions:</b> Inspect and replace the fuel injectors, fuel pump, and oxygen sensors if necessary.</li><li><b>Potential Risks:</b> Delayed repair can result in severe engine damage and reduced fuel efficiency.</li></ul>