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Old 12-16-2011, 12:21 PM   #1
Scooby Newbie
Member#: 291697
Join Date: Aug 2011
Chapter/Region: SCIC
Location: Long Beach, CA
2013 WRX STI Limited
Ice Silver Metallic

Default Easiest way to check for bad o2 sensors?

I am throwing a CEL 0420 for cat threshold. I have checked for exhaust leaks but my IAM is still 11! I have a tactrix cable and romraider for anyone that can help me analyze the data.
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Old 12-16-2011, 11:02 PM   #2
Scooby Newbie
Member#: 3409
Join Date: Jan 2001
Chapter/Region: NWIC
Location: Oly
98 My FMIC
Is bigger than yours.


do a drive cycle, get it up to operating temp then cruise at 50mph for 2 minutes with no loads on, no slowing or speeding up, no hills, then lift off the throttle for 5 seconds and accelerate back to 50, repeat 2 more times.

You'll want to monitor A/F and O2 sensors, speed, throttle position. For the 2 minute stretch you want 5 seconds per division to see how the sensors are reading - steady versus erratic. Then switch it to .5 seconds per division for the decelerate section so you can see if the O2 is reacting faster than the A/F sensor.

Post up what you get.

O2 sensor resistance should drop pretty quickly to about 30 and stay relatively flat. If it's all over the place, there's either a bad sensor or bad wiring.
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Old 12-20-2011, 12:12 AM   #3
Uncle Scotty
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Member#: 16200
Join Date: Mar 2002
OK buy Nates beans


its done....throw it away
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