Yesterday while driving my 1995 850 Turbo my check engine light came on. It came on about twenty minutes into the drive, I was starting to get into to some traffic going into Chicago. This morning I checked the OBI diagnostic and pulled fault code 231, and no others. Based on searching the forum it looked like a vacuum leak could cause the problem.


What should i do to further diagnose the problem? What is the best way to check for vacuum leaks?

2-3-1? thats long term fuel mixture too weak or too rich in part load stage.
your running realy rich and its high enough to trip the com. check that out.
and i found that you can most of the time hear the leak, or use soap water.

when was the last tune up that you had done? probably a while ago, right? get a good one done, bet your air filter is severly dirty.

A normal occurrence with Volvo 850s. Just keep in mind these cars are not brand new any more and many of the parts gradually degrade over time and consequently precise, accurate information to the ECU becomes a bit of a lottery so, just reset your code and wait for the next time for it to come on - it won't be all that long, then simply reset it again.

Or you can take it to the stealer who will charge $$$$'s for probably for a little or no real improvement.

Resetting this light is annoying, but it is the easiest, cheapest and most convenient way of dealing with this rather irritating problem.

If you want to save time and cost in the longer term, replace ALL your vacuum hose with the silicone ones.

Worked for me.
:)