Water in Fuel warning light caused by temperature?

[GR5677]

Can anyone tell me how the WIF sensor is wired on a 2009 CRD? Mine shows the WIF warning every time I drive it for more than 20 minutes, and draining the filter, replacing the sensor and even unplugging the sensor has made no difference to the behaviour at all. The light doesn't come on until the engine is fully up to temperature. Once it has come on, for the first couple of minutes I can usually make it go off temporarily by accelerating hard, though it always comes back on and eventually will stay on until shut down. There are no DTCs that my basic scan tool can pick up.

I'm guessing that there is an issue in the wiring somewhere where there is a short to ground of the WIF sensor being triggered by something else that is temperature dependent. Perhaps the fuel temperature sensor in the filter head? But I can't find a wiring diagram that shows how the WIF and nearby sensors are wired up, so any help would be much appreciated.

 

[KJowner]

I don't have a wiring diagram for the later jeeps. It sounds like a damaged wire somewhere.

 

[GR5677]

I don't have a wiring diagram for the later jeeps. It sounds like a damaged wire somewhere.

The behaviour is strange but completely predictable so it's not something as simple as a frayed wire sometimes shorting out, more like crosstalk from another sensor. But how that could work in practice I have no idea.

I've been doing test runs and from a cold start to first trigger of the light is 12-15minutes. It usually first triggers when slowing down (heading to station of a morning it is normally one of two roundabout entries where it first comes on). For the first few minutes after it triggers hard acceleration will turn it off again, but then by 20 minutes it's on and stays on until restart.

I know that the coolant temperature is already up and stabilised before it comes on so it's a warm engine thing, but beyond that ???

 

[KJowner]

Odd, you say it does the same thing with the sensor unplugged?

 

[GR5677]

Odd, you say it does the same thing with the sensor unplugged?

Yes. I first tried a new sensor, behaviour was the same. So then unplugged it completely, and again behaviour exactly the same.

 

[KJowner]

Weird, wonder if you have any corrosion on the ECU plugs or a bad earth on it.

 

[GR5677]

Weird, wonder if you have any corrosion on the ECU plugs or a bad earth on it.

Having trawled through the service manual the WIF sensor return signal pin is adjacent to the engine oil pressure signal return pin in the ECM connector. I guess oil pressure dropping to a certain point as the oil heats up could be triggering the WIF if there is contamination between the pins? It will be going into workshop in the new year to be fixed under warranty, but it would be nice to know what it is that needs fixing before it goes in!