Ok, so here goes. One day driving home car stalls and will not start. Towed the car home and did some diagnostics.
Replaced the Crankshaft and camshaft position sensors. Car started and ran fine. Took car to work one night and would not start(raining). Went back the next day (dry)and the car started fine. Figured bad wires, rotor and cap, so I replaced them. Car started and ran fine with no codes. Son took car to a friends house and car would not start. Went over tonight and car started and as I was getting ready to leave the engine died. Tried to read the codes and the red light is on dim, Push the button to read the codes and the red light lights up bright and as soon as I release the button the light goes dim but does not flash any codes. If I move the lead to one of the other plugs it will read codes but not in A2.

Any help would be appreciated,

 

Maybe try removing and installing the ECM and see if that helps.
Sometimes they have a bad connection.

 

Was thinking about that. Also what do you think about disconnecting the battery and letting it sit. Just don't know how long to leave the battery disconnected for?

 

I'd inspect all plugs and wires(by plugs and wires I'm referring to electrical harnesses) under the bonnet. Check the male and female connectors to see if the pins are OK. Sounds like an electrical gremlin[:@]

 

The battery might not be a bad idea but make sure you check the ECM connections as well.

 

Ok,
So just got home from the car, stuck at sons friends house, pulled both control units on the right front side and reseated both. Tried to read codes and got nothing. The light is still on dim and not putting out codes. I checked the connections to the crank and camshaft position sensors. Engine still spins like normal but still not starting. I am thinking that the ECU is bad because of the dim red light on the code reader. However I am confused on which module is the ecu. There are two modules in the box on the front right side of the engine compartment. My 850 wagon is a standard non turbo model with 215 thousand miles on the clock. I am upset as it has been a great car and has not given me any problems untill now. The car even has the orginal clutch in it. So whick of the two models is/are the ecu for the car?
Thanks in advance.

 

The engine module says Bosch on it. The transmission one says AW on it.
Also if you can try checking for fuel,spark, and injector pulse.