2005 Titan Tranny Trouble

The first thing I would do would be check the battery and connections. A bad battery or connection can cause loss of power issues. However, it also could be an ECM relay problem. If so, then there wouldn't be any codes. Have you got the recent recall to replace the ECM relay yet? The original relay in the IPDM goes bad and cuts power to the ECM, and the truck loses power intermittently, and sometimes won't start. If you don't have the recall done, you should go get it fixed for free. But you could verify if the ECM relay is bad by swapping the ECM relay with the fog light or rear defrost relay in the IPDM. If this is indeed the cause of your trouble, then when you swap the relay out, the problem will go away and at least you can drive to the dealer and save yourself the tow fee. I wouldn't suggest driving around with your truck shutting down and losing power. A few people have blown their cats by loading them up with fuel due to ECM relay failure. Here's a diagram of the IPDM that shows the location of the ECM relay: