An oft misdiagnosed check engine light on a wide range of Toyota, Lexus and Scions is code P0606- ECM/PCM Processor Malfunction. More often than not, the culprit is NOT the ECM/PCM assembly but rather the sensing or heater circuits in the air/fuel ratio or oxygen sensors. We went more into diagnosing a failed air/fuel ratio sensor in this post. A technician can diagnose the P0606 code fairly easily by checking the freeze frame data out of the ECM/PCM when the problem was detected. Some things to look for include:
- Air/fuel ratio sensor (normally sensor 1) or oxygen sensor (normally sensor 2) heater circuit out of specification for 1-2 frames ONLY. Sometimes the heater circuit will intermittently open or develop high resistance. A resistance of many thousands of Ohms is an indicator of this, or drastic jump in resistance that only last for a few frames of data after the car is warmed up
- Air/fuel ratio sensor or oxygen sensor data is out of range. Toyota air/fuel ratio sensor operate between 0 and 5 volts, oxygen sensors between 0 and 1 volt. Anything above 5 volts indicates a problem that requires further investigation.
- Air/fuel ratio sensor abnormal behavior, not enough to set a “Stuck lean” or “Stuck rich” code, but freeze frame data indicating jumps in voltage quickly for only a few frames (faster than normal response).
If you have a P0606 – ECM/PCM Processor Malfunction code in addition to other check engine P codes (especially if they are air/fuel or oxygen sensor codes), repair the other codes before addressing the P0606. More often than not the P0606 is a false positive.
As Eden Prairie and Chanhassen’s Toyota and Lexus repair specialist, we hope this helps a DIY or auto mechanic alike avoid an unnecessary ECM/PCM replacement!