I have had this problem for a while, I have just had a top end rebuild on a 2003 156 after a cambelt snap. Now you may not agree with me here, but the garage had it for 2 week whilst fixing it, I rang them to see if it was ready and he said "Engine management light was on" (Meaning the dreaded MCSF), I did not tell them about this before it went in!! The garage said "We are putting another Crank Position Sensor on as the the first one didn't work and still was showing the same fault code", got it back yesterday and its dissapeared (For Now), This means my car has had 3 C.P.S in 2 years. My battery is totally dead getting new one today.
This may shed some light, but take my comments with pinch of salt, I always thought it was Lambda Sensors that cause this, obviously not!!