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Discussion Starter · #1 ·
Hello hello! I've been using information on this forum for about 5 months rebuilding a 2002 325xi but this will be my first time posting. Usually, I'm able to search around enough to find my answer but unfortunately not this time around.

I hooked up my bmw computer to the old gal and I'm getting the error from INPA: Downstream Sensor 3 rich voltage not reached

No problem, I need a new O2 sensor, got it. But which one of the 4 is sensor 3?? I tried putting a generic computer on it and got P1144 which the computer didn't understand. After some googling, I've found varying results for the P1144, some of which claim it's bank 2 sensor 2.

Any help would be GREATLY appreciated as I have had my fair share of battles with O2 sensors and will only be changing whichever one is failing. If it's a must, I'll change both in that bank, but I still need to know which bank at least sensor 3 is in according to INPA.

Thanks in advance!
 

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P1144 is O2 Sensor Activity Check Signal Too Low (Bank 1, Sensor 2). From the Bentley Manual.

This is the Bank 1 Post-Cat O2 sensor.

If the engine is not running/idling 100%, not sure I would replace the O2 sensor YET.

The sensor may be bad, but there may be another problem as well.

I am very cautious about replacing O2 sensors where there is any code other than an O2 sensor heater failure code.
 

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Discussion Starter · #5 ·
I'm replacing because it's throwing a CEL and won't pass emissions here with it lit up. Additionally, I get a bit of a rough idle when cold and a smoke test shows no leaks so I'm thinking this might be a culprit. At this point the vehicle runs pretty perfect, but I need to get my stickers so I need to put out the service engine light. Thanks for the heads up on which o2 sensor this is!
 

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Replacing the Post-cat O2 sensor will not likely change the cold rough idle, but I am sure you will know once the sensor is replaced.

If the sensor replacement does not solve the problem, time to buy the OBDFusion App and VeePeak interface for under $30 and start diagnosing.
 
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