This isn't exactly a crank - no start problem with my 2001 Outback (4 cylinder), because the engine actually does start for a second or two, and then it stalls out. I'm getting a diagnostic error code of P1112, and I don't know if that has anything to do with this problem. The car was running great up until now. Any ideas on what this could be, or what my diagnostic sequence should be?

It's a code for the MAP sensor or manifold pressure sensor.

The computer uses input from the pressure sensor to determine fuel mixture and add more or hold back some fuel depending on manifold pressure and atmospheric pressure. If the sensor has failed, it is probably commanding the fuel mixture too lean and is causing the engine to stall shortly after starting. Usually you can simply unplug the sensor and start the engine and see if it runs any better or different.

 

The MAP sensor is a small black square that should be bolted on top of the throttle body or the manifold near the throttle body. Has three wires going to it. Make sure the plug is tight and make sure there is no dirt or corrosion inside the plug. Check the wires leading to the sensor for any damage.

The sensor is held on by two bolts or screws, remove it and check the o-ring seal for damage. Check the end of the nipple on the sensor for obstruction. If it's full of carbony black crud carefully clean it out with electronics cleaner and that may help.

Thanks. I unplugged the sensor, and it still stalls out. Does that mean the problem is elsewhere?

OK, that was a bonehead move on my part. I must have disconnected the knock sensor or something (whatever is right behind the manifold, duh). I disconnected the MAP, and no more stalling. Is that the end of the diagnosis, then? Is it always a bad MAP sensor when disconnecting it stops the stalling?

Did you do the other steps I mentioned? Check wiring? Remove the sensor and check the nipple for carbon buildup?