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Old 03-15-2011, 06:35 PM
Join Date: Mar 2008
Location: Granby, CT
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Default Code PO 172?

My son's 97 850 T5 (turbo) has shown a (generic) CEL code of PO172 which cross references to Volvo code EFI 231 or 232 (fuel trim). Any suggestions on where to start would be appreciated. (O2 sensors seem to be ok- my tool captures live data).

Many thanks
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Old 03-15-2011, 11:03 PM
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1995 Volvo 850
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Every time I have had that code I have found a vacuum line loose from my PTC valve. It's part of the PCV system close to the turbo. Check the line to make sure it's connected and the elbow for a tear.

Item 10 closest to 8 on this pic.
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Old 03-19-2011, 12:59 PM
Join Date: Mar 2008
Location: Granby, CT
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Thanks for the reply, esp. the link to the parts diagram. All the vac. lines and fittings have been replaced within the past year to avoid these types of issues. Checked the fitting you indicated (good, new) as well as all the other vac, hoses/fittings. Did find one hose that seemed a little loose, replaced that, cleared the code, and crossed my fingers. Within a day and approx. 100 miles it was back. Back to the drawing board. Again, thanks.
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Old 03-19-2011, 01:12 PM
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1996 Volvo 850
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172 is almost always a vac issue like rspi said...
did you check the elbows on the manifold and at the pressure regulator?

After a quick google search for some pics, I found this for reference....

Last edited by MattyXXL; 03-19-2011 at 01:15 PM. Reason: Added Link
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Old 03-19-2011, 04:47 PM
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Any driveability issues?

1998 V90, 162k miles.

1983 244 GL
1995 855T
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Old 04-22-2011, 10:06 AM
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Location: Granby, CT
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I know the original post is now a month old, but I want to thank Matty XXL for the tip. The elbow referenced in your link was completely shot. Replaced it, cleared the code, car passed emissions! Many thanks
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172, 1996, 850, 95, 97, code, cross, obd, p0, po, po172, refrence, turbo, volvo, vovlo

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