Technical P0115 Engine Temperature Coolant Circuit

[NIGELOG]

Have on on-going minor problem with Punto Mk2 box van 1.2 8 valve


Usually after 50 miles or so driving the coolant temperature gauge drops to zero (as if receiving no data to record) and triggers the EML.


It will return after a few minutes. I have monitored (via auto doctor pro) the coolant and intake temperature while driving and they remain consistent up until the point the coolant temperature is no longer recordable.


When the signal returns the coolant temperature is always the same as before the dropped signal


This on occasion though has triggered the rad fan although temp reading well below the required temperature


I have tried a few tests as posted on this site and have a few anomalies


1. Although the engine looks identical to all other Mk2 I have seen, I have no separate radiator temperature sensor and no wiring loom to suggest it was ever there


2. If I disconnect the ECT sensor then turn on the ignition it does not trigger the radiator fan


3. Car drives perfectly except for this little quirk but the EML annoying


Any ideas as to how to back trace the likely cause of this. I have multimeter, OBD scanner etc


Any help appreciated

 

[Brendan W]

Sounds to me like the temp sensor is giving up.
Disconnecting the sensor and turning on the ign gives a different result to turning on the ign and disconnecting the sensor in my experience. The first won't put the fan on the second will.

 

[NIGELOG]

Sounds to me like the temp sensor is giving up.
Disconnecting the sensor and turning on the ign gives a different result to turning on the ign and disconnecting the sensor in my experience. The first won't put the fan on the second will.

Thanks Brendan, I'll try that and also test the sensor (when I can find a thermometer). I'll also check for the 5v steady voltage supply. Will replace if any not right

 

[Brendan W]

You might find it tricky to pin down an intermittent fault in the sensor. It seems to be coming and going of it's own accord. Try it anyway - you'll always learn something when you start measuring.
Call me grumpy and cranky but I would just change it out and be done with it even if I wasn't 100% sure. Which is exactly what I blame garages for doing

 

[NIGELOG]

Which is exactly what I blame garages for doing

HaHa, know that sentiment