OBD-II Code P0606 is defined as a PCM Processor Fault
Want does this mean?
The PCM or Power Train Control Module performs many vital functions in a modern vehicle, such as management of the Fuel System, Ignition System, Transmission, Anti-Lock Brake and Traction Control systems. The PCM regularly runs a self-diagnosis function where it performs normal mathmatical calculations, and if the results of these calculations are not as expected, the P0606 code will be set.
When the code P0606 is set in the Powertrain Computer, it means that the Powertrain Computer or PCM is failing its own self-check and has found problems with the CPU (central processing unit ). So, in most cases, the processor itself is defective and the PCM needs to replaced and re-programmed. But, before you replace the PCM, be sure to check for any shorted output devices that may have caused the CPU to fail.
When diagnosing a P0606 code, it is important to record any other codes and the P0606 freeze frame data. Then one should duplicate the code setting conditions with a test drive. Pay close attention to the engine load, throttle position, RPM, and road speed because a P0606 can be difficult to detect.