99 Neon Bad PCM ?

I have a 99 Neon Sport DOHC, It reads a code of 1899 and check engine light on. This is the Park Neutral switch bad. But I just changed it cleared the code
and it comes back in about 10 min. also the temp guage reads good until i start running down the road then it pegs out at hot, ( the engine is not hot or overheating) if you turn off the switch and back on it reads correctly until you start driving again. I have also changed the temp sensor . any help would be appreciated as i am at my wits end. the only thing I can guess is the PCM.
Thanks
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