I have a '94 850 wagon that has twice stalled in the last couple days and was difficult to start this morning. A light not in the manual (upside down green 'y') has come on each stall. The stalls were both while moving, not stopped. Is this an emissions problem? Where should I start looking?

That is your Lambda light. Your car has 2 small boxes in front of the computer box, right next to the windshield washer fluid bottle on the passenger fender. These are OBDII compliant. Learn how to use them and get information from the computer to tell you what is wrong.

The "A" box with the single probe used for both boxes, is for the important parts, tranny, engine, ABS,etc.

http://www.brickboard.com/FAQ/700-900/EngineOBDCodes.htm

and page down about 3 pages to find what you need to learn.

Klaus
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Just driving a 1998 V70R :)

Thanks, Klaus.
I found the diagnostic box, but it was on the right side in front of the washer fluid, not on the left by the shock tower as the webpage explained, ran the test and it came up no fault. I suppose that is a good thing, but it leaves me with no answers and a little worried about hitting the freeway with the family over the holiday weekend. Still searching for answers....

You need to check ports A-1,A-2,A3, etc. They all cannot come up with a 1-1-1. The A-1 port is for the transmission, A-2 is fuel system, A-3 is ABS, A-5 is TCU, and A-6 is ignition. A-7 is the instrument panel, no Lambda light from that port.

If you find a code, write it down and then try to delete it. If it stays deleted, it is an old code and probably has no bearing.

Klaus
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Just driving a 1998 V70R :)

Thanks again,
I think I've narrowed it down to the ignition system. Checked socket #6 and get a 3-1-4 code (NA according to chart) and a 3-2-4 code...not on the chart. Optimistic as seem to be narrowing in on the problem, but frustrated at not finding THE solution. Called Volvo before finding this code and they seem to think it might be a relay problem. They suggested giving a relay near the coolant tank a whack to see if that would prompt a restart and hence locate the problem's source, but there isn't a relay near the coolant resevoir. There are two in front of the radiator unit itself. Perhaps they were referring to one of these.

What Klaus said,

A6 - 314 Camshaft Position sensor (CMP) signal missing or faulty
A6 - 324 Camshaft Position sensor (CMP) signal missing sporadically

324 sound like a corroded connector as the first suspect.

My 850 has a brand new one of those.

Both of your codes point to the camshaft position sensor. The CPS is to the rear of the rotor/cap. Tap that with a screwdriver! But, really, check the electrical connection first.
Remove and replace with new will probably be your option. Try to clear both of those codes first.

Check your timing belt if it is old. Just for kicks.

Klaus

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Just driving a 1998 V70R :)