I'm getting a p0600 Serial Communication Link code on my son's car. I've replaced the brake sensor, Crankshaft Position Sensor and still the BAS Light comes on and then check engine light and his car gets stuck in first gear and won't shift out of it unless I clear the codes and it runs like a charm until it wants to do it again..which is becoming more frequently. I also have a little transmission fluid in the wiring the connects to the TCM sucking in through the wire from the trany. Didn't believe it till I saw it!!! Can I re-program my TCM? Also if the transmission fluid gets worse, any idea how to obtain a used harness that goes from the TCM to the Transmission or even what the name of that is even called? I can only find the engine harness on any search I do for THIS harness... Any help would be MUCH appreciated!!!!!