Water temp sensor woes

[WRXONP]

So ever since I got my ver 2 sti - the check engine light will randomly come on - the trend seemed to e that on idle when the cars fully upto temp the light would come

On and the passenger side fan would come on- and u rev it up and the light went out and fan came off - never came on when driving -

So I pulled fault codes and got 21 which from what I've read is water temp sensor - which makes sense that the fan comes on -

So I pulled intercooler / intake etc and changed that ****y mother ****er - reset ECU with the plugs under the dash - still pulls 21 - did the ole battery dance trick to reset it - still have 21

Now I'm confused because before the symptoms were a lot like a dud water temp

Sensor - sometimes it wouldn't start cold - would just die - since changing the sensor it starts cold perfectly

So a quick question without me pulling it all apart again - is where does the wire got the water temp sensor go? Straight into the loom ? Would it be worth resistance checking the wiring from the plug to the ECU pin?

Another thing is does a Subaru only use water temp for cold start enrichment ? Does the input to ECU at operating temp control the afr ? Because afr is hanging around 11.5 even with the dud sensor

From what I've red however - do u simply plug the blacks and the greens and turn key to on to reset ECU ? Or am I missing something

Cheers

[Rosssub]

Make sure the contacts inside the loom plug are clean, could also check the bigger engine loom plugs near battery are clean and tight. A drop of oil in the wrong spot is enough to short the signal.

AFAIK the ECU constantly monitors the engine temp sensor for cold run/hot run fuelling.

To reset the ECU with the green and black plugs connected you have to drive it until the CEL starts flashing. Then it will either flash a CEL code or constant flashes for all ok.

[WRXONP]

Ahh so I was missing something haha thank you !!! I will try that after work - as since

I have replaced the sensor the cel hasn't come up - when I searched google

It simply said to join plugs and turn key to on - but thank you !