The truck will run but barely. Was on my way home from a hot-shot run the other day. Stopped for a light and the engine sound changed. The gauges were all ok but it sounded louder. The power seemed to be about half or less. It was rush hour and nowhere to get off and check it. When I did, everything seemed ok under the hood, oil, water were ok and checked wires to the sensors. Continued on at a slow pace, we could go 35 up hill and 65 down hill. I was over 200 miles from home and it took a while but we did get home. Got my tuner out to check for codes but there is no power at the plug or data terminal. Tried another tuner and it would not power up either. Worked on it today and replaced the ecm, it runs the same and still doesn't power up the tuner but it did turn the cel light on. Checked all the fuses and all were good. Does anyone know where the data terminal gets it's power, I was wishing for it to be the ecm. Don't think 2 of them would have the same pwoblem. I have all the service manuals that I bought the facxtory service manuals when the truck was new but haven't been able to figure it out. It's stumped me and I really need to be on the road with it. The truck has 440K miles on it and and has never acted like this. Any info would be very much appreciated. Thanks

 

I want to say that the OBD connector gets it's power from one of the IOD fuses, they are in the fuse box on the side of the dash and should be enclosed in a yellow or white plastic cover. If those are good the other thing to look for is grounds, the engine ECU grounds should be on the drivers side of the engine, the chassis ECU ground is normally on the passenger side real close to the pass. side battery. There are also some grounds on the drivers side right on the frame. I'm a little rusty on my 2nd gen driveability so I may be off on some of the locations but those are some of the first things I would look for.

 

I found the problem. Don't know why but both of the Hypertech tuners are dead. They won't light the power light on my truck so I tried them on wife's truck. They don't power up. We tried a friends tuner for the '03 and it worked and gave us the codes. There were four codes listed but the first one was the PO216, that was enough. I have a spare pump and will install this weekend. Will get back with the results, now I need to call and see why both tuners don't work.

 

Make sure you put a fuel pressure gauge on it and see if the lift pump is ok too. Just cause it's running doesn't mean that it is, and it might be what killed your IP.