Transmission pulsing after new radiator install

[MoosePond123]

I installed a new radiator on my 2000 S80 and now a few days later the transmission is pulsing and the check engine light has come on. I did not replace the small amount of fluid that drained out of the radiator when I change it out because the fluid level on the dipstick was high before I started and is still at the top end following the installation. I noticed some bubbling on the dipstick which I assumed was created by the air void created within the radiator when I disconnected the lines.
Is it worth a try replacing the filter and flushing and replacing the transmission fluid, or should I have the car towed to a transmission specialty shop? Could this problem be caused by a faulty radiator where the radiator coolant is seeping into the transmission cooler within the radiator?
Is my transmission cooked or is it possible that a fluid change could resolve this problem?
Thanks.