engine does not turn over or start u1000 code This complaint is about the U1000 fault code locking out the starting of the vehicle. A few months ago the transmission began to shudder when shifting into overdrive at about 50mph. I called a transmission shop and they suggested "shudder-stop" additive to the transmission fluid. At this point the transmission fluid looked fine (nice red color). I added the "shudder stop" and the problem went away for a few weeks. Then one day the truck started driving like it was always in 3rd gear --really slow takeoff and rpm really high. After I researched online and discovered a common problem with coolant getting into the transmission due to a deffective nissan radiator, I checked the transmission dipstick again and found it looked like chocolate milk. I did not want to spend the money for a new transmission and radiator so hoping I had caught it before the damage was too extensive, I choose to flush the transmission and radiator. First I pulled the drain plug at the oil pan and drained about a gallon of very brown foamy contaminated fluid from the transmission. Then I pulled transmission coolant hoses from the bottom of the radiator and directed them straight to the external cooler in front of the radiator. I pluged the lines coming from the radiator to prevent leaking coolant. I disconnected one of the transmission coolant lines and started the pathfinder. While fluid pumped out this hose into a drain bucket, I added fresh transmission fluid to the dipstick hole. I continued to do this until my trany fluid looked clean coming out the hose than shut off the truck and reconnected the hose to the external cooler. I then flushed the radiator. Afterwards I drove the truck for a few days and it drove and shifted fine (just a little shudder once again in overdrive). Then one day last week, the truck would not start. I checked the engine codes with a scanner and found a U1000 fault code. This code is related to the ECM communcation or grounding and will not let the truck start until it is corrected. I have found other info online about coolant contamination at the transmission control module TCM causing this issue. Do not know how to correct at this point.