I have a 2003 S40 1.9T. 79000 miles. Check Engine Light is on. Initially the codes were misfire on all cylinders, lean bank one o2 sensor, MAF sensor, and MAP sensor.... I replaced the spark plugs, MAP sensor, o2 sensor, cleaned the MAF sensor, replaced the fuel filter, cleaned the CVVT solenoid, cleaned the idle air control valve and throttle body, and still the same problem. My codes now read P0131, P0107, and P0101 (same as before without the misfire). O2 sensor code..... again. MAP sensor code again...... and MAF issue again. Fuel pressure checked out ok and no vaccume leaks..... I have only owned the car for a short time and here is the strange part..... 99% of the time it drives perfect. I have had rough idle and a few stalls on occasion. One thing I finally noticed is that when I start it, if it starts good and the idle is not jumping around much, then it will run great until I shut it off again. This could happen ten times in a row no matter how far I drive or how frequent in between stops. Once in a while I will start it and it will idle rough and almost die. If I continue to drive it when it starts off like this, it doesn't improve. Struggles to idle at stop lights and sometimes stalls. If I turn the car off and restart it right away it may run perfect again. I am just not getting it....... My thought is that I need to replace the ecu...... Any thoughts?

 

I believe there are 2 MAP sensors on your car. IIRC there is one on the intercooler and one on the intake manifold under the cover for the fuel rail. Some models have only one but I can't remember what year it changed. I believe they are identical so if you have two then swap their positions, erase the codes, and drive the car to check if anything changes.

If you have the model with only 1 MAP then my next guess would be the MAF since you cleaned it, but did not replace it.

In this photo look between the 2 intake runners on the right. You can just see the black plastic of the MAP sensor:


Now look at this diagram. The MAP is number 3 in the square: