HelloCustomer

I'm sorry to hear your Mazda is having trouble.

The code "PO661" is defined as secondary shutter valve malfuntion.

A shutter valve is a unique part on turbocharged engines. What it does is block airflow from the turbo into the engine after the key is turned 'off'. Since the turbo is still spinning very fast when the car is turned off it can force air into the cylinders moving them or causing damage. If the cylinders are moved the engine will heave a bit, hence the name 'shutter'.

Shutter vavles rarely god 'bad'. It is more likley that you have some other condition causing this problem. The SSV is located in the throttle body of the intake manifold. The easiest and cheapist repair would be to try and clean the SSV and throttle plates using specially made aerosol 'Throttle Body Cleaner' available from any local autoparts store. If this fixes the problem, have your light reset - some autoparts store can do this for you - or wait and it will eventually go away on its own, IF this cleaning fixed the problem.

While your in there, try looking over all the wires leading to the various sensors for loosensess or play.

I hope that helps,
J.D.