Diagnostic codes

I have a p71 police interceptor. I have replaced the transmission solenoids and fluids, but it still show codes p0755 and p0753 and the o/o light flashes when I drive it. Vehicle does shift but not as smooth as I feel it can. No clanking or jumping when it shifts just a hesitation before it shifts to overdrive. I have reset the codes with diagnostic tool, but codes come back after driving it a few miles along with flashing o/o light. I am thinking the ecm is that a possible cause or should I look elsewhere? Is there a way to test the ecm? Thank you.