System Too Lean (Fuel Trim) PO171 lexus possible causes and solution

First inspect the intake to air flow meter rubber tube any cracks loose clamps causing unmetered air to get in. Dirty air flow meter could cause this. What kind of air filter r u using? Cone oiled filters can get oil droplets on the air flow meter. Most operate with in set voltages watched on Data Monotor & technician will floor the car & see what the peak volts are. Another down wind cause is a O2 sensor going bad checked the same way in data monotor with a scanner device. Good Luck

Several common issues you should check first:

- Clogged injectors
- Fuel metering system has a problem somewhere (dirty sensor, loose connection, etc.)
- Vacumn leaks somewhere in the intake system AFTER the metering sensor.
- Bad o2 sensor

anything from say a sensor to a bad gas filter. there is probably a flow chart for diagnosis for the trouble code.

The O2 sensor might be going bad