1. Gather Information:
* Specific Code: Get the exact trouble code (P-code) from your OBD-II scanner. This will be more helpful than just "lean on bank 2." Different codes within that category point to different potential causes.
* Symptoms: Note any other symptoms besides the check engine light. Is there a loss of power? Rough idling? Hesitation? Backfiring? These clues help narrow down the possibilities.
2. Likely Culprits (in order of likelihood):
* Vacuum Leaks: These are extremely common causes of lean codes. Inspect all vacuum lines and hoses, especially those connected to the intake manifold, the brake booster, and the emission control system. Look for cracks, holes, or loose connections. Pay close attention to the areas near Bank 2. A simple visual inspection might not be enough; use a vacuum gauge to test for leaks.
* Mass Airflow Sensor (MAF) Sensor: A faulty MAF sensor provides inaccurate air readings to the engine computer, leading to a lean condition. Cleaning the MAF sensor with MAF sensor cleaner (following the instructions carefully) is a good first step. If cleaning doesn't resolve the issue, replacement might be necessary.
* Oxygen Sensor (O2 Sensor): Bank 2 has its own O2 sensor. A malfunctioning O2 sensor can't accurately measure the oxygen levels in the exhaust, leading to incorrect fuel mixture adjustments. Replace the Bank 2 O2 sensor. They are relatively inexpensive and relatively easy to replace.
* Fuel Injectors: A clogged or faulty fuel injector in Bank 2 will prevent sufficient fuel delivery. Testing fuel injector operation requires specialized tools, often best left to a mechanic.
* Fuel Pressure Regulator: This regulates the fuel pressure in the fuel rail. A faulty regulator can cause low fuel pressure, leading to a lean condition.
* Fuel Pump: A weak fuel pump might not be able to supply enough fuel under demand. Testing fuel pressure is needed to diagnose this.
3. Troubleshooting Steps:
1. Visual Inspection: Start with a thorough visual inspection of all vacuum lines, hoses, and connections associated with Bank 2. Pay attention to the area around the intake manifold.
2. Clean the MAF Sensor: Clean the MAF sensor with a MAF sensor cleaner.
3. Check for Vacuum Leaks: Use a vacuum gauge or your ear to listen for hissing sounds near vacuum lines. Spray a carb cleaner around suspected leaks (with the engine running); a change in engine RPM indicates a leak.
4. Check Fuel Pressure: If you suspect a fuel delivery problem, have the fuel pressure tested.
5. Replace the O2 Sensor (Bank 2): This is often a cost-effective solution, and a failing O2 sensor is a common culprit.
6. OBD-II Scanner Monitoring: While the engine is running, use your OBD-II scanner to monitor the short-term and long-term fuel trims. Large positive numbers indicate a lean condition. This can help you track down the problem area.
4. When to Seek Professional Help:
If you're not comfortable performing these diagnostic steps or repairs yourself, take your Explorer to a qualified mechanic. They have the tools and expertise to properly diagnose and repair the issue. Ignoring a lean condition can lead to engine damage.
Important Note: Remember that Bank 2 is usually the passenger side bank on a Ford Explorer. Always consult your repair manual for specific location diagrams. Safety first! Disconnect the battery negative terminal before performing any electrical work.
