01 450. Cuts back to idle while driving, water in fuel light, SES, Wait to start lights all come on for about 3 seconds. Ive tried cleaning the connections, unplugging 1 sensor at a time and still nothing. I put a scope on it and its not losing 5v reference. When im driving it only does it when the engine fan comes on and keeps doing it until the fan turns off. Water in fuel light, SES, and wait start light all come on. if I let off the pedal and get back on it, it comes up to about 2k and cuts again. Any suggestions?

 

Could be quite a few things, but some common things to check are the engine wiring harness at the driver's side valve cover, a little ways from the large square connector that is connected to the bracket that holds the air intake tube. The harness tends to rub on the valve cover and short out the wiring.

Also, check to make sure that the heating element inside the fuel filter housing isn't loose. Usually this blows a fuse, but I have seen a few that would just touch momentarily and throw things off.

Does it still have the original windshield? Very common for windshield leaks to allow water to drip down on the back of the fuse panel under the dash. Look for corrosion and water stains there.

 

I think you might want to check the connections where the PCM relay plugs in. In fact, check all three relays (Fan, IDM and PCM).

 

Welcome to FTE, ATS.

I'm going to move your thread over to the 1999-2003 7.3L Power Stroke Diesel engine forum, to see if we can get you some help.

 

The truck only has 64k on it. I have checked the wiring harness, and looked under the dash and didnt see any water stains. I will check the heating element today.


Its a mechanical fan, Thats why I dont understand why this only does it when the fan is on. I already checked and cleaned the connections at the relays. I tried doing everything I could before making a post.

 

Oh I see...I thought you meant the climate control fan.
That is puzzling...when the engine fan locks up it pulls a ton of extra air. The only thing I can think of is that when the fan is moving that much extra air it's causing some of the wires to move about and causing your issue. It kinda sounds like the PCM is losing power and starting back up again (hence the WTS and SES lights). This is why I was thinking about checking the relays Next things to check are the various ground points....there is one just ahead of the oil cooler on the block that might be subject to a bunch of air flow when the fan locks up...

Do you know how to check for voltage drop across the negative side of the electrical system? If not, here is a good set of videos for reference.
BBB Industries - How-to Video Center

I also ran across a 4 part video that talks about voltage drop in more detail.

Good luck. I hope you find the solution soon and hopefully it's a simple fix.

 

Just a WAG, but check your ignition, if it is not getting good contact it will freak out and do that... I say that because I was on Facebook last night reading some group postings on the Powerstroke group page, and the kids were talking about turning the ignition past on just a little to disable the speed limiter, it shuts down everything but the engine supposedly. Sounds like what is happening in your instance, only it might be just getting occasional bad contact. Might be worth a shot.