CEL came back on on my 98 Rav. I checked it with my Innova code reader and found out that I had P0171 again "System too lean". I had the same problem last May and posted it here. Fault Code P0171 and P1133
Last time the problem seemed to go away on its own after I cleared the fault, but not this time.
I pulled the spark plugs and found out that just like last time when I had this code was that the engine is actually running too rich. Freeze frame data showed that the STFT has gone +24% and the LTFT has gone to +44% meaning that the ECM is calling for full fuel. It is my understanding that when the short term fuel trim goes to it's max value, calling for fuel, then the fault code P0171 will be set.
This RAV4 has the Calf. emissions package so the first sensor is a A/F sensor.
I checked the A/F sensor's heater resistance and it was in spec. I would hate to go out and buy a new A/F sensor without being sure that it has failed. An opinions??