Hi Maggy,
I had the same error codes, P0600. It was the CAN BUS - the splice at S116 had failed. Unfortunately, S116 is located in the harness under the brake booster - impossible to get to without taking apart the braking system, so I jumpered a twisted pair from the instrument cluster can bus to the shift lever assembly can bus and that solved my problem. It sounds like you issue is currently intermittent. Mine became permanent such that the car would not crank. I wrote up my experience tracing the fault in the CAN BUS and you can find it in the forum. It's not for the faint of heart.
-Jerry