Hello,
I recently had my eclipse go into limp mode where there transmission stays in R and 2nd gear. I took it down to AutoZone and they read a P0705 Transmission Range Sensor (AKA Neutral Switch) and P1600 Serial Communication Link. I changed the Nuetral Switch and its still in limp mode. I took it down to Autozone again and the only code left is the P1600. I've searched a ton of things, but can't seem to find any good info out there. I've also taken the eclipse to an AMCO shop and their scan took couldn't communicate with the car. The best thing I can come up with is maybe the TCM or ECU. Any ideas would be appreciated.
Thanks,
Mark

 

By the way, this is a 2.4L non turbo.

 

When my Montero Sport went into limp mode I took it to a repair shop. They said it was showing a p1600 code and needed a new TCM. They replaced the TCM for over $800 and it works fine. I realize now that I could have easily put a new TCM in for about $39 from ebay. Mine is located under the driver side dash against the firewall. Two connectors and two bolts are all that has to be connected/disconnected with no need for programming. See if you can find a replacement on ebay and where your's is located.