System Fault 128 Water Sensor Problem

[craigcaf]

I've just been replacing the coolant hoses on my T350 with a set of silicone hoses from Power. Also at the same time I used the opportunity to change both water temp sensors with new items also from Power. Both sensors were working however the dash temp was pretty inaccurate and for a few pounds seemed reasonable to replace both sensors whilst the system was drained down. Put it all back together and am now getting System Fault 128 Water Sensor and the Dash is reading 0degC constantly for water temperature.

Here's what I have tried - for the ECO water sensor unplugging the sensor causes the fans to come on, which I assume is the default response for an open circuit failed switch. Also tried plugging the old ECU sensor back in (without it in the block) and again the same. Fans off with engine cool and fans come on when the old sensor is unplugged. This all seems to be normal behaviour to me so I have assumed that the problem is with the dash water temp sensor.

Again I have unplugged the new one and connected the old one whilst leaving it out of the block (the old one was working, but just inaccurate). This makes no difference and I still see a Fault 128 when switching off then back on and the dash still indicates 0degC. I don't know if the switches need a good earth, I would have thought that they do not need earth, but anyhow have tried also earthing them with a wire. No effect.

So at the moment I have System Fault 128 which I can't get rid of. Any ideas what this might be?

Interestingly I notice that I still get an air temperature reading with the air temperature sensor disconnected (air bod off) - would have though I would have got an error there.

Thanks

[craigcaf]

And the answer is.... there are two plugs on the loom which the dash water temp sensor plug can connect with. I stupidly connected it back to the wrong one. The correct plug had dropped down underneath the wires and I missed it. In my defence the sensor has a red and blue wire, one plug has a red and blue wire and one has a black and blue. It's the black and blue one that is the right one.

Anyhow all spot on now.

C

[ShiDevil]

craigcaf said:

And the answer is.... there are two plugs on the loom which the dash water temp sensor plug can connect with. I stupidly connected it back to the wrong one. The correct plug had dropped down underneath the wires and I missed it. In my defence the sensor has a red and blue wire, one plug has a red and blue wire and one has a black and blue. It's the black and blue one that is the right one.

Anyhow all spot on now.

C

Pleased you got it sorted and well done for giving it a go yourself