I had posted in another thread that I was looking at some confusing multiple indications on my OBD-I 95 5-speed car. I thought I would post here a couple of thoughts. This car has the separate ignition and fuel injection computers.

What led to the confusion was I had a bunch of cam sensors lying around, and I installed a bad one. The car started, and then later it cut off and stranded me.

This led to a faulty/missing cam sensor signal code (3-1-4). The tach dropped to zero. Just a bit of useless info there. Troubleshooting with codes:
http://www.volvoclub.org.uk/tech/ser...s-NonTurbo.pdf

What I wanted to mention here is how well testing these sensors works. If you read this:
http://www.volvoclub.org.uk/tech/ser...sicTesting.pdf

It says that the middle wire on the cam sensor switches from zero to 5 volts every cam rotation. This is really easy to check. I don't have a breakout box, so I put a straight pin through that wire and clamped my voltmeter on there. Sure enough, it was bad. I could also simulate with the sensor off the car by putting a flat bladed screwdriver between the magnet and whatever the sensor is. It sure is simple, and no oscilloscope needed.

In general, that "basic testing" document is great for a no start, but nobody talks about it much.

If you have ECM wiring trouble, there is a point where you could save a lot of work by having a breakout box, but I don't see me ever having one for a volvo.