ODBII Error Code p1620. Can anyone help me diagnose what this could be?

[ThatTinTin]

Hi Everyone, new member here.

Have just bought a 2000 (W Reg) 2.4L S80 with 101,000 miles on the clock. Bought at a bargain price as it had some issues and as I am not working at the moment I need something to keep me busy.

So, so far i have managed to clean the ECM, which was pretty grotty, I am replacing the brake sensor when it comes in the post in the next few days, I am also replacing the front suspension mounts as they are making a very heavy knocking sound when i go over a bump (I thought at first it was the S80 standard exhaust knock when I test drove it). I bought a kit to pull out a few shopping trolly dings on the bodywork and I have totally refurbished the leather, carpets and head lining, replacing the headlining on the A and B pillars as they were peeling off.

I still have a couple more things to do, but there is one thing that is annoying me at the moment, I get an ODBII error p1620, which seems to relate to cooling but I cant find anymore information other than that. I have trawled forums and google and not found anything specific for Volvos (NB: My ODB meter doesnt have a Volvo setting so I use the VW setting as I think I read somewhere the engines on the early S80s were made by VW?).

I have checked coolant levels, the main fan, pipes. I haven't removed the thermostat yet but the temp gauge in the car is not going higher than half way so I dont think its that.

Has anyone come across a similar problem before and if so how did they fix it.

(The only other codes i have had have been related to the brake switch height, brake bulb, ECM usuals and every now and then a car alarm error but I think thats a ghost error).

[Legofan]

Trouble Code: P1620 - (Manufacturer Specific)
System: Powertrain
Subsystem: Computer and Auxiliary Output Circuits

DTC Description: Engine Coolant Temperature (ECT) Signal open / short to B +

Location:
Analysis:
Likely Cause: Circuit Open or Short to Battery Positive