Front O2 sensor question - wrx 02

Front O2 sensor question - wrx 02

Postby adecan » Tue May 28, 2013 8:23 am


I have a lot to write. I’ll try to be brief.

I own a wrx 02. I had the p0031 code and the first thing I did was installing a new sensor (denso 234-9011) but the code still on. Then I tried to follow the diagnostic procedure from the service manual. There are the images for the DTC P0031:

First of all I measured the battery voltage. I’m reading 11.80 V with engine off and 13.90 with engine on.

Step1: Done. Te code still on

Step 2: I’m reading 11.0 V with switch on (engine off).

Step 3: I’m reading 1.0 ohms aprox. between each terminal and chassis ground.

Step 4: Clearly I don’t have a “Subaru Select Monitor” so I plugged the tactrix and logged with Romraider. I have no reading of front AF sensor current. Neither have a reding of front AF sensor Voltage and the front AF ratio is stocked at 14.7 no matter what.

Step 5 and 6: Reading 13.8 V in both terminals.

Step7: reading 5.8 Ohms with cold engine and 7.2 Ohms when it’s hot. According the service manual it has to be under 10 Ohms but I’ve read from other threads that it must vary between 1 and 2 Ohms.

But the code still on…

I'm kinda neewe here so I need some extra help. I will follow your suggestions and sharing the results. Please don't leave me alone. I'm in Venezuela and the nearest dealer is about 500 mile from my city.

Thanks in advance
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