Dear Doctor: My 2009 Toyota Camry with 199,600 miles has a check engine light showing the codes P0101 and P0170. I have already replaced the MAF sensor, PCV valve, throttle body, the car's computer, O2 sensors, cam sensor, crank sensor, fuel pump, injectors, and fuel pressure regulator. I also checked for multiple vacuum or air leaks, and the cabin air filter, spark plugs, alternator, and battery have all been checked over the course of a year. Now the car has both codes showing consistently and it shakes at idle. What should we do? - Cheyenne
Dear Cheyenne: The engine has a lean condition, or at least is telling the computer it is running lean. The first step is to find out when the computer set the fault code, the engine speed, and temperature and gas pedal position. The problem could be a faulty front air ratio sensor and rear 02 sensor - and both always need replacement together. Identifix shows multiple trouble test details on these codes, and identified a repair diagnosis to one owner's car as the ground wire on the mass air flow sensor circuit.