C4 picasso P0118 fault

[bigdaz74]

Hi got big problem C4 Picasso 1.6Hdi 2009 car starts no problem but engine temp too high with temp symbol use diagbox and got the P0118 which says permanent fault short circuit to positive or open circuit and a BSI code 7155 coolant temp data fault. What we have done so far
1 tested ECT sensor` ohms working with heat and cooling
2 This is the problem tested voltage and shows 12v not 5v. So getting over 7 voltage more
3 Followed white wire from sensor to engine bay fuse box where it connects to plug and changes to pink wire which goes to big block of wires that connect to BSM fuse board in engine bay which is giving 12v
4 Live data shows engine temp 255c before engine even started with or without ECT connected . Start car and fans come on straight away as temp says high

Any help would be great before going to auto electrician

UPDATE spoke to 2 auto electricians said to much hassle to trace fault so wont touch it.
Tried another BSM identical model numbered to see if that was shorted . No change

So I'm stuck on wiring problem which I cannot find wiring diagram or possible ECU fault any advice would be great as stuck on this for days

[THEO2002]

Hi
Did you find a solution??
I have the same problem.

[GiveMeABreak]

You've probably got a faulty coolant temperature sensor:

Fault Code:	P0118
Description of Fault:	Engine coolant temperature signal: Open circuit or short circuit to the plus. The fault occurs if the voltage of the signal from the engine coolant temperature sensor is higher 4.9 Volts, corresponding to a temperature of -40°C, for more than 500 ms.
Conditions for Fault to clear:	Ignition on
Downgrade Modes whilst Fault is active:	Cutting off of the air conditioning The ECU stops the regulation of the EGR valve The ECU stops the regulation of the EGR butterfly The ECU cuts the regulation of the bypass mixer Deactivation of the additional heating
Symptoms:	Diesel fuel consumption a bit higher Engine overheating with illumination of the engine coolant temperature indicator light Lack of power
Suspect Areas:	Coolant temperature sensor Electrical harness Engine ECU