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Discussion Starter · #1 ·
Hi all. 3 weeks ago I bought this 2006 S40 for what I thought was a pretty good deal.

Since then I've replaced the alternator and AC belts, shimmed the AC clutch, and replaced the coolant hose assembly. This forum has been my go-to resource and I want to say thanks, and ask for your help on this next repair.

Last week the CEL came on, so I had my dealer (non-Volvo) scan it. It returned as a bad fuel rail pressure sensor. I looked up the repair and decided to do it myself since it wasn't warrantied. I bought this part on Amazon which is actually a BOSCH part and though Amazon says it doesn't fit the S40, some reviews said it did. It has one of the same part numbers on it as the sensor I pulled off the car.

Right after I installed the new sensor, the engine seemed to run a little quieter. I took it out for about a 4 mile drive at highway speeds and everything was great. Later that day, the CEL came on again. This time I got the generic code P0171 - Powertrain system too lean. After some research, I see that this is relatively common in these cars.

I plan on replacing the fuel rail pressure sensor with the original one and clearing the code to see if it goes away and returns with the fuel pressure sensor code. That would tell me I got the wrong part. Other than that, I don't think I have the PCV problem, at least if I do it's not presenting like it does in the Youtube videos I've seen of it. A common cause of this code seems to be an air leak. Where are common places to check for that?

If anyone has any insight or experience with this, I'd appreciate some tips on where to go next. Thanks!
 

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If you want peace of mind or even a trouble-free running car for years to come, always use Genuine Volvo parts. I have and there is never any second-guessing.
The part he bought is the exact same part that Volvo uses. My guess is either a faulty new part or something else has gone wrong.

The car can also start running rich or lean with faulty O2 sensors.
 

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... Or the FPS was failing for a long time & the new "normal" parameters are way off the old. Try resetting the ECU to base & see what happens. Disconnect battery leads & touch together for a few seconds.
 

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Discussion Starter · #5 ·
Thanks for your replies.

I put the older sensor back on, but while doing so, also cleaned off the MAF sensor. While doing that, I found that the hose leading to the MAF sensor had slightly slipped off its housing. I properly secured it and tightened the hose clamp. Now I'm just getting the original fuel rail pressure sensor code. I am still working on finding the problem. Going to put the new pressure sensor back on and see if that helps it tonight.

THanks again for the replies. I'll update this tomorrow.
 

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Discussion Starter · #6 ·
Update: Last night I put the new pressure sensor back on and cleared the CEL light. After my to-and-from work commute today, the CEL light has not come back on. My OBD reader doesn't show any pending faults as of now. Hopefully this will take care of it.
 
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