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Just had a check engine light stay on for the past couple of trips on my '03 Aero. Read the code as P1141, which as I understand it, refers to the rear/downstream (post-cat) oxygen sensor. The car drives fine presently, and accelerates as expected. Is replacing the rear oxygen sensor likely a simple fix for this code?

I'll be able to order the part in and work on the car some time within the next month. In the meantime, will not replacing the rear oxygen sensor for a long period of time cause any issues for me driving the car (in terms of damage, excess fuel usage, fouling spark plugs etc.)? Or is this more an emissions thing?
 

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Hi AeroChris,

Mimmi's "maybe" response quite correct - you need some more data to identify the issue .

I suggest that you get yourself a logging OBDII tool and log data for your O2 sensors, front and rear. I have not needed to do this (yet) on the two 9-5's I currently maintain, but I have had to on my 2005 BMW.

The two Apps I am most familiar with are Torque and OBD Fusion. I have ODB Fusion and I use it with an iPhone and a VeePeak bluetooth OBDII addapter. You can set up to log specific PID's (such as O2 sensor 1 and O2 sensor 2), start from cold and idle it until warm (4 minutes minimum), and see how the sensor voltages change.

The cool thing about the data logs is that you can email yourself a CSV file with the logged data and look at your sensor response(s) on your laptop, tablet, or phone - you can plot them or whatever you like. Sensor 1 data are used to control air and fuel - Sensor 2 data are USUALLY only to tell whether the catalytic converter is working properly. Running with a bad sensor 2 probably won't hurt much - but I would not because any CEL that is constantly on means I might miss the critical CEL error that I won't see because the light is already on. The OE Bosch sensor can be had for about $62 to $80 USD.

Is the 1141 code intermittent ? If it is, AND if you have data logs that suggest the catalytic converter is 'lazy' but the sensor is good, then try a bottle of Techron Concentrate ($4.79 at my Walmart) in your next full tank of gasoline. With a borderline cat, clean injectors might be the thin margin that avoids the CEL.

Hope this helps you
 

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Those logging apps are great. That's how I diagnosed the rear O2 sensor issue on my NG900. I used a cheap Bluetooth OBDII dongle and the Torque app on my phone. I had it display a voltage graph, and it was pretty obvious that the sensor wasn't doing much of anything. The line was way too close to flat. Once I replaced it, the graph showed the correct voltage swings.
 
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