Hey there!
has anyone had this happen to them before???
I have my ECL on in my 03 wrx sti. Managed to borrow a scan tool to retrieve the fault code which is P0031 front o2 sensor (off manifold) heater control circuit low, bank 1 sensor 1.

So I bought a aftermarket 02 sensor to suit, (bosch). I've fitted it and cleared the code, and it hasn't made any difference. Light comes on after a minute when car is started and is the same fault code. I've correctly rewired all the terminals to the new sensor (not soldered either). Checked continuity from plug connector in engine bay to new wiring connecter on every wire. Checked that the sensor is getting power. Even disconnected other o2 sensor to make sure it was the right 1... Made sure I have the right part for the model car. Checked all fuses, even tho theres nothing stating A/F or o2 sensor..
Has anyone got any other suggestions to add??? Please help...

I've been told you should use the OEM sensors. (Probably just the plug that's different) I was going to use a Bosch, but ended up using a Subaru one when i had a P0037 (rear 02) and CEL cleared no worries and didn't come back.

Where did you fit the o2 sensor?

It could be the front afr sensor on the headers for your my03?

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[SIGPIC][/SIGPIC]
Should have bought an STI

hey richard, cheers for the feedback, I fitted the new sensor before the cat.

Maybe I should've gone genuine 02 sensor part now... thinking it's maybe got a different resistance in the heater circuit??

Do you know if they have a relay in the wiring circuit???

Cheers Sheree

You have to use a genuine Subaru Air/Fuel Ratio sensor. Nothing else will work.
Most aftermarket sensor's are o2 sensor's, which are different from Air/ratio sensors.
You need the part number for the genuine part, you may be able to search it and get it cheaper on Ebay or something. New from SUbaru they are around 650-700 dollars.
Try Evolution R, they have some available, cheaper because they're not in a box with Subaru written on it. you just need the part number.

EDIT: bank 1, sensor 1 is the front Air/Fuel sensor, before the turbo

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Its just the internet dude, its not real.
F.B. Racing
01 WRX (STI badged)
2010 XR5 Focus
06 Impreza Hatch 2.0i

Hey johnvk7

Really???? I was tryna keep costs down... Guess sometimes going genuine is always best.. Thanks for the heads up tho - Cheers Sheree