OBD-II DTC Technical Description
Fault in the PCM / ECM Processor
What does that signify?
This diagnostic trouble code (DTC) is a standard powertrain code that is applicable to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
This code is relatively simple. It indicates that the PCM/ECM (powertrain/engine control module) has detected an internal integrity fault in the PCM.
When this code is triggered, it should store freeze-frame data that can provide information about the vehicle’s condition at the time the P0606 code was activated.
Symptoms
The most common symptom of a P0606 DTC code is the illumination of the “Check Engine Light” or MIL (Malfunction Indicator Lamp).
Photo of a PCM with the cover removed:

Causes
In all likelihood, the PCM/ECM has malfunctioned.
Possible Solutions
As a vehicle owner, there is little you can do to resolve this code. The most common solution for a P0606 code is to replace the PCM, although in some cases, re-flashing the PCM with updated software may fix the issue. It is recommended to check for any Technical Service Bulletins (TSBs) related to your vehicle.
In all likelihood, the solution is to replace the PCM. This is generally not a DIY task, although it may be possible in some cases. It is strongly advised to have a qualified repair shop or technician perform the work, especially one that can reprogram the new PCM. Installing the new PCM may require special tools to program the vehicle’s VIN (vehicle identification number) and/or anti-theft information (PATS, etc.).
NOTE: This repair may be covered under the emissions warranty, so it is recommended to check with your dealer as it may be covered beyond the bumper-to-bumper or powertrain warranty period.
Other PCM DTC codes: P0600, P0601, P0602, P0603, P0604, P0605, P0607, P0608, P0609, P0610.