02 regal tranny problems

Hello all.
New to the forum here, my 02 regal has been acting strange the past few days. normal driving seems ok. but under hard acceleration the trans won't shift unless i let off the throtle. or if i need to step on like to pass someone. now if i stay on the throttle i hear a rattleing or a tapping noise that comes from the front. ( the best way to discribe it, it sounds like an old 4cly climbing a big hill with bad gas and the valves are going to coming flying out of the valve cover) my service engine soon light flashes a few times and then goes out. it just started happening all of the sudden. i have checked some of the treads on here and it seems like it might be the PCS. but i'm not sure. it has 56,000 miles on it and the tranny was flushed and serviced at 48,000 miles. the trans code os m15 which is the 4t65e transmission. any suggestions?

thanks, charlie

Welcome to AF.

Engine conditions will affect how the tranny will work. Since you have a flashing SES light you should get it scanned to see if any emissions or tranny related DTCs are stored. When the SES light flashes it indicates a misfire condition most likely secondary ignition related. Spark plugs and ignition wires to start.

Also, is your Regal a LS or GS model?

it is an LS