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Old 04-12-2015, 06:53 PM   #1
mopar3.0
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Member#: 261696
Join Date: Oct 2010
Chapter/Region: E. Canada
Location: st johns nl
Vehicle:
2004 wrx
red

Default front oxygen sensor got my stumped

04 wrx
just re installed engine and all that jazz,
car runs fine but throws p0031 for front 02 sensor

ive been thought the FSM and all the wiring seems fine, Tried a good used o2 sensor i had on hand,

In Romraider the sensor logs fine for about 5 seconds and then goes static at 14.7

The heaters in both sensors read 1.3 ohms(Fsm said less then 10 is Ok)
I even ran solid power to the heater circuit to the heater.

Possible i have 2 bad sensors?
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Old 04-12-2015, 07:52 PM   #2
mopar3.0
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Vehicle:
2004 wrx
red

Default

it appears the ecu is dropping the ground circuit after a few seconds running,
it starts to flash and shuts off

Edit i turned off the p0031 dtc in rom raider and wired the ground solid and it still stops reading, Order a new sensor in am !

Last edited by mopar3.0; 04-12-2015 at 08:20 PM.
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Old 04-13-2015, 12:26 AM   #3
Uncle Scotty
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there is a fuse that controls this, iirc its sbf-5...maybe

look in the underhood fuse box...test fuses with a meter
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Old 04-14-2015, 06:14 PM   #4
mopar3.0
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Join Date: Oct 2010
Chapter/Region: E. Canada
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Vehicle:
2004 wrx
red

Default

new sensor same problem, power supply and fuses still good,
guess its a ecu

Time to disable closed loop lol!

Last edited by mopar3.0; 04-14-2015 at 06:41 PM.
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Old 04-15-2015, 10:56 AM   #5
jmdolphin
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Chapter/Region: MWSOC
Location: grand rapids, MI
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rally blue

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ecu is always a last resort. seems stupid but trace wires from o2 sensor to ecu first.
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Old 04-15-2015, 04:11 PM   #6
mopar3.0
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im going to dig into it again tonight, it worked fine last season lol
alos noticed my batt voltage in romraider is only around 13v and my fluke reads 14.7
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Old 04-15-2015, 05:29 PM   #7
wrxfool
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Join Date: Oct 2005
Chapter/Region: W. Canada
Location: Edmonton, Alberta
Vehicle:
2015 STi
ISM

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I actually threw this code and P0037 when I went stage two on my 2015 STi on Sunday. Happened after about 30 miles of driving. Changed out my rear O2 sensor and still have the same issues.

Can't find the heater circuit fuse anywhere. It used to be under the glove box on previous Gen models.

I'll let you know if I find anything.

Good luck.
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Old 04-15-2015, 06:28 PM   #8
mopar3.0
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found a a resistor on the ecu with broken solder joins, repaired that and it worked for few minutes and stopped again, bat voltage came up to 14 and back to 13 again!
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Old 04-15-2015, 07:02 PM   #9
Uncle Scotty
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yeah....ditch the ecu
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Old 04-15-2015, 07:45 PM   #10
mopar3.0
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2004 wrx
red

Default

soldered back on, then found the brown plug on intake manifold harness corroded. clean and tighten pins and so far so good
ecu reading 14v
FIXED!

Last edited by mopar3.0; 04-15-2015 at 07:52 PM.
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Old 04-15-2015, 09:53 PM   #11
wrxfool
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Location: Edmonton, Alberta
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ISM

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Cobb heat shield was touching the wiring harness and one of the wires got spliced a little. Moved the harness out of the way and voila! Going to repair the wire tomorrow and bend the heat shield out of the way.
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