ECU and Water in fuel light!

So I have an 04 lowboy that I love like a baby. But just had my first snafu. Driving down the road and down she goes ecu light and water in fuel light simultaneously come on and she is stalled no restart. Being a "man" I pop open the hood actually go as far as removing the filter and reinstalling it still no start. So here comes the flat bed and off to the dealership where I can already feel the pain:bash:. Later that day I get the call that it was the oil high pressure switch that went bed causing a 12 volt charge to the ecu where there shouldn't be and now I need one of both. EXPENSIVE:eek: So I was wondering if anyone else has heard of this happening? Any ways to prevent or any preventative maintenance?


06 T1N Can
I have heard about the water in the fuel filter, but not the 12V to the ECU.

Reading the service manual, the oil level sensor is fed 5V and for 12V to be present a wire could've been shorted to 12V.
Yeah it seemed strange to me but it all fell under warranty so life is good!!:rad:
Dealer says there are more problems now the water in fuel light won't go out and dealer said they have to manually program my ecu but my key isn't working. So they have to get me a new key which means my autostarter won't work anymore :thumbdown: any ideas on the water in fuel light?


and his elephants
This is similar to what happened in '08 to my 2005 2500HC 118", except the water in fuel light would go out occasionally afterward. This problem and the dealer's solution ate my stimulus check that year. My issues were triggered by a bump on the speed control lever, and the dealer never caught that. There's a short somewhere but I've learned to live with it.

When one of these beasts stalls and you have dash lights glow, check all the fuses (particularly the 25 amp ECU fuse at the steering column) before you call for the tow truck. :professor:
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Thanks for the post! I have to wait 5 days to get a key from Germany and they say it won't even start because of this light. So I am sorta sitting and waiting as patiently as I can ( major A.D.D ) UGHH! Then the best part is they don't know if the new key will fix the problem but it's just an additional problem! Anyone else heard of this little problem?:thinking:
Here we go, apparently the dealer can't get the water in fuel light to go out it. Here is the problem: Start van the light comes on and stays on, if you shut it off and restart it after it ran for a couple of minutes the light doesn't come on and doesn't until the next time you go to start it. But the best part is they are charging me 900.00 dollars for that fun little diagnosis and all they did was part change until they ran out of parts to change!! Any suggestions on where to go from here and do I have a legit beef with the dealer here?:thinking:


New member
This $900 trail and error wasn't lumped in with the warranty work. ???????

Kind of makes you want to keep one of those miniature recorders in your pocket, trail and error doesn't work, put them parts back on the shelf
My sprinter is home and that makes me happy but the fact the water in fuel light won't go out is not great.
If I turn on the ignition to ON and turn it off then start like normal no light if I try to just start it like normal water in fuel
light stays on the whole time!! I don't care as long as it won't be a problem later on, like perhaps getting water in the fuel and
running it anyway because I won't know any better. Looking for any suggestions, the dealer changed the sensor to the filter and the
wiring to it. HELP:idunno:


New member
Just shooting in the dark here, but what happens when you disconnect the electric plug from the water in fuel sensor? Also, can you see that they really replaced the wiring and sensor as they claimed?

Hey thanks for the response's guys and yeah they changed wiring and sensor nothing they also tested the fuel and said no problem. They believe it's in the "bus" system like a 2.5 to a 3 volt system that talks to the modules but I don't know anything about that system. That is why when you turn the key on and off the light will not come on. These guys seemed pretty honest so I think they are just lost on this problem. I am soliciting any ideas.


New member
To me, all monies spent on the poke and hope diagnostics should be refunded. Unless they forewarned you that this could happen, I would demand the money back.

So here is the latest and greatest on this situation. Currently still dealing with Water In Fuel light being on. (stage left) Welcome DAD! I was hoping I would be able to track down the culprit with my new DAD.

I scanned the CDI it gave me the water in fuel light sensor code. So I cleared it, turned key off and on came right back. So I checked Instrument cluster it showed a MOD1 Bosch was not functioning so I cleared that and then retried CDI before turning van off and on, and CDI was clear until I turn the van off and on again. So my thinking is I have a bad MOD1 just like the DAD says and it may be whats kicking the light on. Now to you gents where are these mods located and since I do have the 05 manual can I find it in that? Sorry if this question is to simple and I am just missing the obvious.:idunno:

This DAD is so cool
Oh yeah one more thing is it possible the transistor on the instrument cluster that is tied into the Water in fuel light circuit went bad during the original problem and how bad is the process to remove the cluster to check it?
Hey thanks Sikwan !

Do you or anyone else know how to get a map of the pc board for the cluster so I can test the transistor? My light does not blink. So it's probably the mod 1 that the DAD says is bad, anyone know where that is located and if its just a matter of swapping it out. The dealer did say they put a new ECU in when they did the work so I am assuming that the problem is not there...


06 T1N Can
Do you or anyone else know how to get a map of the pc board for the cluster so I can test the transistor?
You most likely can't get a schematic. What I have done is to work backwards from the LED by looking at the copper traces.

There are only three components to deal with; PWR, resistor, LED, transistor, GND. Any one of the three components in bold between PWR and GND can be in rearranged depending on the type of transistor and how the designer was feeling that day with the resistor and LED.

Find the transistor and test for a LED to GND short. I forget whether it's a BJT or MOSFET. My best guess is it's a mosfet tied to GND.

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