Weirdest Electrical Problem I ever Seen S40 06'
 

I really need help,

Two days ago I found the key error message, before even put the key in, then I put the key in, turned it and the car start up just fine.

At home, I turned off the key, pulled key out and the engine kept running for 5 or 10 more seconds, the dash board, radio, lights everything stay on. Tried to turn it back on, and didn't start, moved the key form 0,I,II,II multiple times and nothing changed, I had to disconnect the battery.

The immobilizer message came off a couple of time, but seem like the trick of close the open the door 5< times with the small key do the trick and the immobilizer message turned off.

After googling for my problem, I thought the problem was the SCU, starter control module, AKA ignition switch. I just replaced the switch and nothing changed.

This freak car still with all lights on, cluster, radio, and don't start. The remote FOB don't work either. Very frustrating problem.

This is a very well maintained volvo with only 23k in five years.

Thank you.

Edit:
Today I verified all plugs, code CEM-1A41 still there.

Solved:
After many hours I found the culprit of the communication problem DTC CEM-1A41. I found water "just few drops" and a minor corrosion in the top right connector of the CEM. I dissembled the CEM clean up the contacts and the problem disappears, I didn't found the source of the water so I added lithium grease in all the top connectors.

Has this problem returned? I had this same problem a few weeks ago on my 2005 s40. I took it in to my mechanic, not a dealer but a volvo specialty shop. They replaced the wire harness, apparently some wires were cracked and corroded, which also blew a couple of insignificant fuses. this seemed to solve the issue but today after work i had the same problem.

sorry, i'm not very technically inclined, what is the CEM? central electrical module? that's purely a guess. I just have a feeling the mechanic is going to charge me another full day of labour trying to figure this out. I called a dealership asking if they've seen this and they have not. extreemly frustrating and making me question why i spent the money on a volvo.

thanks!!

My Solution
 

Fix for Volvo S40 no power whatsoever, not even dash lights or door locks, key stuck in ignition at position 1: I did all I could find: checked fuses, CEM, move shifter/**** button etc. I did work if jumped, but would not otherwise and key was stuck. Then I held + and - battery cables together as I hear this resets the computer; yet the battery had been out for weeks so not sure if that mattered. And, the battery was only at 230 crank power out of 700. So I replaced the battery and it appears to be fixed. Apparently if the battery is sub-par the computer reads that and just shuts the whole car down 100%; not even dash lights. I could have been the cable cancel but my hunch is it was the battery. And they say new batteries only last 3 years now so be forewarned- carry cables and your mechanical key or you will be locked out and/or stuck.

My Solution