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Over from the UKLegacy forums as I know quite a lot of you kiwis and aussies and have the tt leggys too! Was wondering if someone can shed some light on an issue im having.
Car has been running like sh1t- poor fuel economy, lumpy acceleration, lumpy on idle when started from hot, struggles to stay alive as the revs want to drop.
Plugged in SSM cable and front o2 sensor voltage was reading 0.000v. Cleaned the plug... still nothing. Replaced the sensor with a bosch universal 3 wire and its still showing 0.000v. Jumps to about .02v for a split second when the throttle is pressed but instantly drops back to 0v.
When I test the black signal wire at the plug where the sensor joins the loom, there is 0.45v at idle (this is about right as this would suggest a normal AFR). This suggests the sensor is working and reading accurately. At the ecu however, the voltage is different.
Service manual says that at the ecu plug, the o2 should see between 2.3-2.8v (iirc) . At the ecu pin, mine showed 0.80v with the car idling and o2 sensor unplugged. When plugged in, it jumped to 1.1v but fluctuated massively (down to about 0.6v when revved in neutral and back up to 1+ but never as high as 2v+.
I tested the pins on the loom-side plug on the car to see if they were getting power. The heater wire pin was easy to identify as it was getting a solid 12v. The other white was the ground but was still getting like 0.5v. The signal wire itself was also getting about 0.38v which I found a bit strange but I dont understand enough about auto electrics to make sense of it.
I tried bypassing the entire wiring to see if it was a wiring fault but didnt make much headway. I ran pins from all 3 ports on the o2 sensor plug. The heating elements went straight to the battery positive and negative terminals to simulate the 12v and the ground. The signal wire was ran directly from the 02 plug inside the car and alligator clipped to a paperclip jammed in the back of the 02 signal wire at the ecu. On ssm it showed a constant .330v (usually what a broken o2 will show). It would not move despite revving the car and stank of fuel due to it telling the car its was running a lean mix.
Took it to a garage today and the lad was adamant that I should start with an oem sensor as universal ones are bad for subarus apparently. They dont agree with universal sensors etc. This wouldn't be an issue but the oem sensors are like £180/$250+ and im a student lol. Is there anything else I can try before buying one?
This is the second universal bosch o2 inside 8 months, this is the reason Im worried it isnt the actual fault of the sensor. Im fairly confident there is something else weird going on with the ecu/wiring.
Any help is much appreciated, thank you troops
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